diff --git a/src/black_white.py b/src/black_white.py
index 494818a..d7f7bc4 100644
--- a/src/black_white.py
+++ b/src/black_white.py
@@ -2,14 +2,14 @@
 
 
 def setup_black_white_lists(
-    blacklist_library: str,
-    whitelist_library: str,
-    blacklist_library_type: str,
-    whitelist_library_type: str,
-    blacklist_users: str,
-    whitelist_users: str,
-    library_mapping=None,
-    user_mapping=None,
+    blacklist_library: list[str] | None,
+    whitelist_library: list[str] | None,
+    blacklist_library_type: list[str] | None,
+    whitelist_library_type: list[str] | None,
+    blacklist_users: list[str] | None,
+    whitelist_users: list[str] | None,
+    library_mapping: dict[str, str] | None = None,
+    user_mapping: dict[str, str] | None = None,
 ):
     blacklist_library, blacklist_library_type, blacklist_users = setup_x_lists(
         blacklist_library,
@@ -40,53 +40,44 @@ def setup_black_white_lists(
 
 
 def setup_x_lists(
-    xlist_library,
-    xlist_library_type,
-    xlist_users,
-    xlist_type,
-    library_mapping=None,
-    user_mapping=None,
-):
+    xlist_library: list[str] | None,
+    xlist_library_type: list[str] | None,
+    xlist_users: list[str] | None,
+    xlist_type: str | None,
+    library_mapping: dict[str, str] | None = None,
+    user_mapping: dict[str, str] | None = None,
+) -> tuple[list[str], list[str], list[str]]:
+    out_library: list[str] = []
     if xlist_library:
-        if len(xlist_library) > 0:
-            xlist_library = xlist_library.split(",")
-            xlist_library = [x.strip() for x in xlist_library]
-            if library_mapping:
-                temp_library = []
-                for library in xlist_library:
-                    library_other = search_mapping(library_mapping, library)
-                    if library_other:
-                        temp_library.append(library_other)
+        out_library = [x.strip() for x in xlist_library]
+        if library_mapping:
+            temp_library: list[str] = []
+            for library in xlist_library:
+                library_other = search_mapping(library_mapping, library)
+                if library_other:
+                    temp_library.append(library_other)
 
-                xlist_library = xlist_library + temp_library
-    else:
-        xlist_library = []
-    logger(f"{xlist_type}list Library: {xlist_library}", 1)
+            out_library = out_library + temp_library
+        logger(f"{xlist_type}list Library: {xlist_library}", 1)
 
+    out_library_type: list[str] = []
     if xlist_library_type:
-        if len(xlist_library_type) > 0:
-            xlist_library_type = xlist_library_type.split(",")
-            xlist_library_type = [x.lower().strip() for x in xlist_library_type]
-    else:
-        xlist_library_type = []
-    logger(f"{xlist_type}list Library Type: {xlist_library_type}", 1)
+        out_library_type = [x.lower().strip() for x in xlist_library_type]
+
+        logger(f"{xlist_type}list Library Type: {out_library_type}", 1)
 
+    out_users: list[str] = []
     if xlist_users:
-        if len(xlist_users) > 0:
-            xlist_users = xlist_users.split(",")
-            xlist_users = [x.lower().strip() for x in xlist_users]
-            if user_mapping:
-                temp_users = []
-                for user in xlist_users:
-                    user_other = search_mapping(user_mapping, user)
-                    if user_other:
-                        temp_users.append(user_other)
+        out_users = [x.lower().strip() for x in xlist_users]
+        if user_mapping:
+            temp_users: list[str] = []
+            for user in out_users:
+                user_other = search_mapping(user_mapping, user)
+                if user_other:
+                    temp_users.append(user_other)
+
+            out_users = out_users + temp_users
 
-                xlist_users = xlist_users + temp_users
-        else:
-            xlist_users = []
-    else:
-        xlist_users = []
-    logger(f"{xlist_type}list Users: {xlist_users}", 1)
+        logger(f"{xlist_type}list Users: {out_users}", 1)
 
-    return xlist_library, xlist_library_type, xlist_users
+    return out_library, out_library_type, out_users
diff --git a/src/connection.py b/src/connection.py
index 0afaaeb..ce4192b 100644
--- a/src/connection.py
+++ b/src/connection.py
@@ -1,4 +1,5 @@
 import os
+from typing import Literal
 from dotenv import load_dotenv
 
 from src.functions import logger, str_to_bool
@@ -9,24 +10,26 @@
 load_dotenv(override=True)
 
 
-def jellyfin_emby_server_connection(server_baseurl, server_token, server_type):
-    servers = []
+def jellyfin_emby_server_connection(
+    server_baseurl: str, server_token: str, server_type: Literal["jellyfin", "emby"]
+) -> list[tuple[Literal["jellyfin", "emby"], Jellyfin | Emby]]:
+    servers: list[tuple[Literal["jellyfin", "emby"], Jellyfin | Emby]] = []
 
-    server_baseurl = server_baseurl.split(",")
-    server_token = server_token.split(",")
+    server_baseurls = server_baseurl.split(",")
+    server_tokens = server_token.split(",")
 
-    if len(server_baseurl) != len(server_token):
+    if len(server_baseurls) != len(server_tokens):
         raise Exception(
             f"{server_type.upper()}_BASEURL and {server_type.upper()}_TOKEN must have the same number of entries"
         )
 
-    for i, baseurl in enumerate(server_baseurl):
+    for i, baseurl in enumerate(server_baseurls):
         baseurl = baseurl.strip()
         if baseurl[-1] == "/":
             baseurl = baseurl[:-1]
 
         if server_type == "jellyfin":
-            server = Jellyfin(baseurl=baseurl, token=server_token[i].strip())
+            server = Jellyfin(baseurl=baseurl, token=server_tokens[i].strip())
             servers.append(
                 (
                     "jellyfin",
@@ -35,7 +38,7 @@ def jellyfin_emby_server_connection(server_baseurl, server_token, server_type):
             )
 
         elif server_type == "emby":
-            server = Emby(baseurl=baseurl, token=server_token[i].strip())
+            server = Emby(baseurl=baseurl, token=server_tokens[i].strip())
             servers.append(
                 (
                     "emby",
@@ -50,8 +53,12 @@ def jellyfin_emby_server_connection(server_baseurl, server_token, server_type):
     return servers
 
 
-def generate_server_connections():
-    servers = []
+def generate_server_connections() -> (
+    list[tuple[Literal["plex", "jellyfin", "emby"], Plex | Jellyfin | Emby]]
+):
+    servers: list[
+        tuple[Literal["plex", "jellyfin", "emby"], Plex | Jellyfin | Emby]
+    ] = []
 
     plex_baseurl = os.getenv("PLEX_BASEURL", None)
     plex_token = os.getenv("PLEX_TOKEN", None)
@@ -120,7 +127,6 @@ def generate_server_connections():
 
     jellyfin_baseurl = os.getenv("JELLYFIN_BASEURL", None)
     jellyfin_token = os.getenv("JELLYFIN_TOKEN", None)
-
     if jellyfin_baseurl and jellyfin_token:
         servers.extend(
             jellyfin_emby_server_connection(
@@ -130,8 +136,8 @@ def generate_server_connections():
 
     emby_baseurl = os.getenv("EMBY_BASEURL", None)
     emby_token = os.getenv("EMBY_TOKEN", None)
-
     if emby_baseurl and emby_token:
+
         servers.extend(
             jellyfin_emby_server_connection(emby_baseurl, emby_token, "emby")
         )
diff --git a/src/emby.py b/src/emby.py
index 62f6fcb..436069e 100644
--- a/src/emby.py
+++ b/src/emby.py
@@ -1,5 +1,5 @@
 from src.jellyfin_emby import JellyfinEmby
-from packaging.version import (parse, Version)
+from packaging.version import parse, Version
 
 
 class Emby(JellyfinEmby):
diff --git a/src/functions.py b/src/functions.py
index 8abb3cd..1e76a26 100644
--- a/src/functions.py
+++ b/src/functions.py
@@ -62,7 +62,7 @@ def log_marked(
 
 # Reimplementation of distutils.util.strtobool due to it being deprecated
 # Source: https://github.com/PostHog/posthog/blob/01e184c29d2c10c43166f1d40a334abbc3f99d8a/posthog/utils.py#L668
-def str_to_bool(value: any) -> bool:
+def str_to_bool(value: str) -> bool:
     if not value:
         return False
     return str(value).lower() in ("y", "yes", "t", "true", "on", "1")
@@ -84,7 +84,7 @@ def contains_nested(element, lst):
 
 
 # Get mapped value
-def search_mapping(dictionary: dict, key_value: str):
+def search_mapping(dictionary: dict[str, str], key_value: str) -> str | None:
     if key_value in dictionary.keys():
         return dictionary[key_value]
     elif key_value.lower() in dictionary.keys():
@@ -100,8 +100,10 @@ def search_mapping(dictionary: dict, key_value: str):
 
 
 # Return list of objects that exist in both lists including mappings
-def match_list(list1, list2, list_mapping=None):
-    output = []
+def match_list(
+    list1: list[str], list2: list[str], list_mapping: dict[str, str] | None = None
+) -> list[str]:
+    output: list[str] = []
     for element in list1:
         if element in list2:
             output.append(element)
@@ -146,3 +148,11 @@ def future_thread_executor(
                 raise Exception(e)
 
     return results
+
+
+def parse_string_to_list(string: str | None) -> list[str]:
+    output: list[str] = []
+    if string and len(string) > 0:
+        output = string.split(",")
+
+    return output
diff --git a/src/jellyfin.py b/src/jellyfin.py
index d9ce6ef..4c0bcda 100644
--- a/src/jellyfin.py
+++ b/src/jellyfin.py
@@ -1,5 +1,5 @@
 from src.jellyfin_emby import JellyfinEmby
-from packaging.version import (parse, Version)
+from packaging.version import parse, Version
 
 
 class Jellyfin(JellyfinEmby):
diff --git a/src/jellyfin_emby.py b/src/jellyfin_emby.py
index c99574d..d8f4387 100644
--- a/src/jellyfin_emby.py
+++ b/src/jellyfin_emby.py
@@ -2,10 +2,10 @@
 
 import traceback, os
 from math import floor
-from typing import Union
+from typing import Literal
 from dotenv import load_dotenv
 import requests
-from packaging.version import (parse, Version)
+from packaging.version import parse, Version
 
 from src.functions import (
     logger,
@@ -22,39 +22,6 @@
 generate_locations = str_to_bool(os.getenv("GENERATE_LOCATIONS", "True"))
 
 
-def get_guids(server_type, item):
-    if item.get("Name"):
-        guids = {"title": item.get("Name")}
-    else:
-        logger(f"{server_type}: Name not found in {item.get('Id')}", 1)
-        guids = {"title": None}
-
-    if "ProviderIds" in item:
-        guids.update({k.lower(): v for k, v in item["ProviderIds"].items()})
-    else:
-        logger(f"{server_type}: ProviderIds not found in {item.get('Name')}", 1)
-
-    if "MediaSources" in item:
-        guids["locations"] = tuple(
-            [x["Path"].split("/")[-1] for x in item["MediaSources"] if "Path" in x]
-        )
-    else:
-        logger(f"{server_type}: MediaSources not found in {item.get('Name')}", 1)
-        guids["locations"] = tuple()
-
-    if "UserData" in item:
-        guids["status"] = {
-            "completed": item["UserData"]["Played"],
-            # Convert ticks to milliseconds to match Plex
-            "time": floor(item["UserData"]["PlaybackPositionTicks"] / 10000),
-        }
-    else:
-        logger(f"{server_type}: UserData not found in {item.get('Name')}", 1)
-        guids["status"] = {}
-
-    return guids
-
-
 def get_video_status(server_video, videos_ids, videos):
     video_status = None
 
@@ -104,7 +71,13 @@ def get_video_status(server_video, videos_ids, videos):
 
 
 class JellyfinEmby:
-    def __init__(self, server_type, baseurl, token, headers):
+    def __init__(
+        self,
+        server_type: Literal["Jellyfin", "Emby"],
+        baseurl: str,
+        token: str,
+        headers: dict[str, str],
+    ):
         if server_type not in ["Jellyfin", "Emby"]:
             raise Exception(f"Server type {server_type} not supported")
         self.server_type = server_type
@@ -123,7 +96,13 @@ def __init__(self, server_type, baseurl, token, headers):
         self.users = self.get_users()
         self.server_name = self.info(name_only=True)
 
-    def query(self, query, query_type, identifiers=None, json=None):
+    def query(
+        self,
+        query: str,
+        query_type: Literal["get", "post"],
+        identifiers: dict[str, str] | None = None,
+        json: dict | None = None,
+    ) -> dict | list[dict]:
         try:
             results = None
 
@@ -173,19 +152,21 @@ def query(self, query, query_type, identifiers=None, json=None):
             )
             raise Exception(e)
 
-    def info(self, name_only: bool = False, version_only: bool = False) -> Union[str | Version]:
+    def info(
+        self, name_only: bool = False, version_only: bool = False
+    ) -> str | Version | None:
         try:
             query_string = "/System/Info/Public"
 
-            response = self.query(query_string, "get")
+            response: dict = self.query(query_string, "get")
 
             if response:
                 if name_only:
-                    return f"{response['ServerName']}"
+                    return response.get("ServerName")
                 elif version_only:
-                    return parse(response["Version"])
-                
-                return f"{self.server_type} {response['ServerName']}: {response['Version']}"
+                    return parse(response.get("Version"))
+
+                return f"{self.server_type} {response.get('ServerName')}: {response.get('Version')}"
             else:
                 return None
 
@@ -193,7 +174,7 @@ def info(self, name_only: bool = False, version_only: bool = False) -> Union[str
             logger(f"{self.server_type}: Get server name failed {e}", 2)
             raise Exception(e)
 
-    def get_users(self):
+    def get_users(self) -> dict[str, str]:
         try:
             users = {}
 
@@ -210,7 +191,45 @@ def get_users(self):
             logger(f"{self.server_type}: Get users failed {e}", 2)
             raise Exception(e)
 
-    def get_libraries(self):
+    def get_guids(self, item: dict):
+        guids: dict[str, str | tuple[str] | dict[str, bool | int]] = {}
+
+        if item.get("Name"):
+            guids["title"] = item.get("Name")
+        else:
+            logger(f"{self.server_type}: Name not found in {item.get('Id')}", 1)
+            guids["title"] = None
+
+        if "ProviderIds" in item:
+            guids.update({k.lower(): v for k, v in item["ProviderIds"].items()})
+        else:
+            logger(
+                f"{self.server_type}: ProviderIds not found in {item.get('Name')}", 1
+            )
+
+        if "MediaSources" in item:
+            guids["locations"] = tuple(
+                [x["Path"].split("/")[-1] for x in item["MediaSources"] if "Path" in x]
+            )
+        else:
+            logger(
+                f"{self.server_type}: MediaSources not found in {item.get('Name')}", 1
+            )
+            guids["locations"] = tuple()
+
+        if "UserData" in item:
+            guids["status"] = {
+                "completed": item["UserData"]["Played"],
+                # Convert ticks to milliseconds to match Plex
+                "time": floor(item["UserData"]["PlaybackPositionTicks"] / 10000),
+            }
+        else:
+            logger(f"{self.server_type}: UserData not found in {item.get('Name')}", 1)
+            guids["status"] = {}
+
+        return guids
+
+    def get_libraries(self) -> dict[str, str]:
         try:
             libraries = {}
 
@@ -218,7 +237,7 @@ def get_libraries(self):
             users = self.get_users()
 
             for _, user_id in users.items():
-                user_libraries = self.query(f"/Users/{user_id}/Views", "get")
+                user_libraries: dict = self.query(f"/Users/{user_id}/Views", "get")
                 for library in user_libraries["Items"]:
                     library_id = library["Id"]
                     library_title = library["Name"]
@@ -299,7 +318,7 @@ def get_user_library_watched(
                         )
 
                         # Get the movie's GUIDs
-                        movie_guids = get_guids(self.server_type, movie)
+                        movie_guids = self.get_guids(movie)
 
                         # Append the movie dictionary to the list for the given user and library
                         user_watched[library_title].append(movie_guids)
@@ -370,7 +389,7 @@ def get_user_library_watched(
                             episode["UserData"]["Played"] == True
                             or episode["UserData"]["PlaybackPositionTicks"] > 600000000
                         ):
-                            episode_guids = get_guids(self.server_type, episode)
+                            episode_guids = self.get_guids(episode)
                             mark_episodes_list.append(episode_guids)
 
                     if mark_episodes_list:
diff --git a/src/main.py b/src/main.py
index 07b56a1..116d75f 100644
--- a/src/main.py
+++ b/src/main.py
@@ -1,10 +1,12 @@
 import os, traceback, json
+from typing import Literal
 from dotenv import load_dotenv
 from time import sleep, perf_counter
 
 from src.library import setup_libraries
 from src.functions import (
     logger,
+    parse_string_to_list,
     str_to_bool,
 )
 from src.users import setup_users
@@ -17,7 +19,10 @@
 load_dotenv(override=True)
 
 
-def should_sync_server(server_1_type, server_2_type):
+def should_sync_server(
+    server_1_type: Literal["plex", "jellyfin", "emby"],
+    server_2_type: Literal["plex", "jellyfin", "emby"],
+) -> bool:
     sync_from_plex_to_jellyfin = str_to_bool(
         os.getenv("SYNC_FROM_PLEX_TO_JELLYFIN", "True")
     )
@@ -91,24 +96,26 @@ def main_loop():
     dryrun = str_to_bool(os.getenv("DRYRUN", "False"))
     logger(f"Dryrun: {dryrun}", 1)
 
-    user_mapping = os.getenv("USER_MAPPING")
-    if user_mapping:
-        user_mapping = json.loads(user_mapping.lower())
-        logger(f"User Mapping: {user_mapping}", 1)
+    user_mapping = os.getenv("USER_MAPPING", "")
+    user_mapping = json.loads(user_mapping.lower())
+    logger(f"User Mapping: {user_mapping}", 1)
 
-    library_mapping = os.getenv("LIBRARY_MAPPING")
-    if library_mapping:
-        library_mapping = json.loads(library_mapping)
-        logger(f"Library Mapping: {library_mapping}", 1)
+    library_mapping = os.getenv("LIBRARY_MAPPING", "")
+    library_mapping = json.loads(library_mapping)
+    logger(f"Library Mapping: {library_mapping}", 1)
 
     # Create (black/white)lists
     logger("Creating (black/white)lists", 1)
-    blacklist_library = os.getenv("BLACKLIST_LIBRARY", None)
-    whitelist_library = os.getenv("WHITELIST_LIBRARY", None)
-    blacklist_library_type = os.getenv("BLACKLIST_LIBRARY_TYPE", None)
-    whitelist_library_type = os.getenv("WHITELIST_LIBRARY_TYPE", None)
-    blacklist_users = os.getenv("BLACKLIST_USERS", None)
-    whitelist_users = os.getenv("WHITELIST_USERS", None)
+    blacklist_library = parse_string_to_list(os.getenv("BLACKLIST_LIBRARY", None))
+    whitelist_library = parse_string_to_list(os.getenv("WHITELIST_LIBRARY", None))
+    blacklist_library_type = parse_string_to_list(
+        os.getenv("BLACKLIST_LIBRARY_TYPE", None)
+    )
+    whitelist_library_type = parse_string_to_list(
+        os.getenv("WHITELIST_LIBRARY_TYPE", None)
+    )
+    blacklist_users = parse_string_to_list(os.getenv("BLACKLIST_USERS", None))
+    whitelist_users = parse_string_to_list(os.getenv("WHITELIST_USERS", None))
 
     (
         blacklist_library,
@@ -219,7 +226,7 @@ def main_loop():
 def main():
     run_only_once = str_to_bool(os.getenv("RUN_ONLY_ONCE", "False"))
     sleep_duration = float(os.getenv("SLEEP_DURATION", "3600"))
-    times = []
+    times: list[float] = []
     while True:
         try:
             start = perf_counter()
diff --git a/src/plex.py b/src/plex.py
index cb4b2d9..116fcd7 100644
--- a/src/plex.py
+++ b/src/plex.py
@@ -295,7 +295,11 @@ def update_user_watched(user, user_plex, library, watched_videos, dryrun):
             watched_movies_ids,
         ) = generate_library_guids_dict(watched_videos)
 
-        if not watched_movies_ids and not watched_shows_ids and not watched_episodes_ids:
+        if (
+            not watched_movies_ids
+            and not watched_shows_ids
+            and not watched_episodes_ids
+        ):
             logger(
                 f"Jellyfin: No videos to mark as watched for {user.title} in library {library}",
                 1,
@@ -362,7 +366,9 @@ def update_user_watched(user, user_plex, library, watched_videos, dryrun):
                 if watched_show_episodes_status:
                     for plex_episode in plex_show.episodes():
                         watched_episode_status = get_video_status(
-                            plex_episode, watched_episodes_ids, watched_show_episodes_status
+                            plex_episode,
+                            watched_episodes_ids,
+                            watched_show_episodes_status,
                         )
                         if watched_episode_status:
                             if watched_episode_status["completed"]:
@@ -385,7 +391,9 @@ def update_user_watched(user, user_plex, library, watched_videos, dryrun):
                                 msg = f"Plex: {plex_show.title} {plex_episode.title} as partially watched for {floor(watched_episode_status['time'] / 60_000)} minutes for {user.title} in {library}"
                                 if not dryrun:
                                     logger(msg, 5)
-                                    plex_episode.updateTimeline(watched_episode_status["time"])
+                                    plex_episode.updateTimeline(
+                                        watched_episode_status["time"]
+                                    )
                                 else:
                                     logger(msg, 6)
 
diff --git a/src/users.py b/src/users.py
index 3c3e68e..a659cdd 100644
--- a/src/users.py
+++ b/src/users.py
@@ -1,15 +1,22 @@
+from typing import Literal
+from plexapi.myplex import MyPlexAccount
+from src.emby import Emby
+from src.jellyfin import Jellyfin
+from src.plex import Plex
 from src.functions import (
     logger,
     search_mapping,
 )
 
 
-def generate_user_list(server):
+def generate_user_list(
+    server: tuple[Literal["plex", "jellyfin", "emby"], Plex | Jellyfin | Emby]
+) -> list[str]:
     # generate list of users from server 1 and server 2
     server_type = server[0]
     server_connection = server[1]
 
-    server_users = []
+    server_users: list[str] = []
     if server_type == "plex":
         for user in server_connection.users:
             server_users.append(
@@ -22,9 +29,13 @@ def generate_user_list(server):
     return server_users
 
 
-def combine_user_lists(server_1_users, server_2_users, user_mapping):
+def combine_user_lists(
+    server_1_users: list[str],
+    server_2_users: list[str],
+    user_mapping: dict[str, str] | None,
+) -> dict[str, str]:
     # combined list of overlapping users from plex and jellyfin
-    users = {}
+    users: dict[str, str] = {}
 
     for server_1_user in server_1_users:
         if user_mapping:
@@ -49,8 +60,10 @@ def combine_user_lists(server_1_users, server_2_users, user_mapping):
     return users
 
 
-def filter_user_lists(users, blacklist_users, whitelist_users):
-    users_filtered = {}
+def filter_user_lists(
+    users: dict[str, str], blacklist_users: list[str], whitelist_users: list[str]
+) -> dict[str, str]:
+    users_filtered: dict[str, str] = {}
     for user in users:
         # whitelist_user is not empty and user lowercase is not in whitelist lowercase
         if len(whitelist_users) > 0:
@@ -64,11 +77,12 @@ def filter_user_lists(users, blacklist_users, whitelist_users):
     return users_filtered
 
 
-def generate_server_users(server, users):
-    server_users = None
-
+def generate_server_users(
+    server: tuple[Literal["plex", "jellyfin", "emby"], Plex | Jellyfin | Emby],
+    users: dict[str, str],
+) -> list[MyPlexAccount] | dict[str, str] | None:
     if server[0] == "plex":
-        server_users = []
+        plex_server_users: list[MyPlexAccount] = []
         for plex_user in server[1].users:
             username_title = (
                 plex_user.username if plex_user.username else plex_user.title
@@ -78,22 +92,30 @@ def generate_server_users(server, users):
                 username_title.lower() in users.keys()
                 or username_title.lower() in users.values()
             ):
-                server_users.append(plex_user)
+                plex_server_users.append(plex_user)
+
+        return plex_server_users
     elif server[0] in ["jellyfin", "emby"]:
-        server_users = {}
+        jelly_emby_server_users: dict[str, str] = {}
         for jellyfin_user, jellyfin_id in server[1].users.items():
             if (
                 jellyfin_user.lower() in users.keys()
                 or jellyfin_user.lower() in users.values()
             ):
-                server_users[jellyfin_user] = jellyfin_id
+                jelly_emby_server_users[jellyfin_user] = jellyfin_id
 
-    return server_users
+        return jelly_emby_server_users
+
+    return None
 
 
 def setup_users(
-    server_1, server_2, blacklist_users, whitelist_users, user_mapping=None
-):
+    server_1: tuple[Literal["plex", "jellyfin", "emby"], Plex | Jellyfin | Emby],
+    server_2: tuple[Literal["plex", "jellyfin", "emby"], Plex | Jellyfin | Emby],
+    blacklist_users: list[str],
+    whitelist_users: list[str],
+    user_mapping: dict[str, str] | None = None,
+) -> tuple[list[MyPlexAccount] | dict[str, str], list[MyPlexAccount] | dict[str, str]]:
     server_1_users = generate_user_list(server_1)
     server_2_users = generate_user_list(server_2)
     logger(f"Server 1 users: {server_1_users}", 1)
diff --git a/test/test_black_white.py b/test/test_black_white.py
index 1ede818..b72d5b8 100644
--- a/test/test_black_white.py
+++ b/test/test_black_white.py
@@ -48,6 +48,7 @@ def test_setup_black_white_lists():
     assert return_blacklist_users == ["user1", "user2"]
     assert return_whitelist_users == ["user1", "user2"]
 
+
 def test_library_mapping_black_white_list():
     blacklist_library = ["library1", "library2"]
     whitelist_library = ["library1", "library2"]
diff --git a/test/validate_ci_marklog.py b/test/validate_ci_marklog.py
index 830c172..263bde3 100644
--- a/test/validate_ci_marklog.py
+++ b/test/validate_ci_marklog.py
@@ -128,8 +128,7 @@ def main():
 
     expected_locations = expected_emby + expected_plex + expected_jellyfin
     # Remove Custom Movies/TV Shows as they should not have guids
-    expected_guids = [item for item in expected_locations if "Custom" not in item ]
-
+    expected_guids = [item for item in expected_locations if "Custom" not in item]
 
     expected_write = [
         "Plex/JellyPlex-CI/jellyplex_watched/Custom Movies/Movie Two (2021)",
@@ -171,7 +170,7 @@ def main():
         "Jellyfin/Jellyfin-Server/JellyUser/Custom Movies/Movie Three (2022)",
         "Jellyfin/Jellyfin-Server/JellyUser/Custom TV Shows/Greatest Show Ever (3000)/S01E03",
         "Jellyfin/Jellyfin-Server/JellyUser/Movies/Tears of Steel",
-        "Jellyfin/Jellyfin-Server/JellyUser/Shows/Monarch: Legacy of Monsters/Parallels and Interiors/4"
+        "Jellyfin/Jellyfin-Server/JellyUser/Shows/Monarch: Legacy of Monsters/Parallels and Interiors/4",
     ]
 
     # Expected values for the mark.log file, dry-run is slightly different than write-run