Fix type annotation for xml_to_string

lib/galaxy/util/__init__.py

@@ -391,7 +391,7 @@ def parse_xml_string_to_etree(xml_string: str, strip_whitespace: bool = True) ->
     return ElementTree(parse_xml_string(xml_string=xml_string, strip_whitespace=strip_whitespace))
 
 
-def xml_to_string(elem: Element, pretty: bool = False) -> str:
+def xml_to_string(elem: Optional[Element], pretty: bool = False) -> str:
     """
     Returns a string from an xml tree.
     """
@@ -1080,21 +1080,25 @@ def string_as_bool_or_none(string):
 
 
 @overload
-def listify(item: Union[None, Literal[False]], do_strip: bool = False) -> List: ...
+def listify(item: Union[None, Literal[False]], do_strip: bool = False) -> List:
+    ...
 
 
 @overload
-def listify(item: str, do_strip: bool = False) -> List[str]: ...
+def listify(item: str, do_strip: bool = False) -> List[str]:
+    ...
 
 
 @overload
-def listify(item: Union[List[ItemType], Tuple[ItemType, ...]], do_strip: bool = False) -> List[ItemType]: ...
+def listify(item: Union[List[ItemType], Tuple[ItemType, ...]], do_strip: bool = False) -> List[ItemType]:
+    ...
 
 
 # Unfortunately we cannot use ItemType .. -> List[ItemType] in the next overload
 # because then that would also match Union types.
 @overload
-def listify(item: Any, do_strip: bool = False) -> List: ...
+def listify(item: Any, do_strip: bool = False) -> List:
+    ...
 
 
 def listify(item: Any, do_strip: bool = False) -> List:
@@ -1153,7 +1157,8 @@ def unicodify(  # type: ignore[misc]
     error: str = "replace",
     strip_null: bool = False,
     log_exception: bool = True,
-) -> None: ...
+) -> None:
+    ...
 
 
 @overload
@@ -1163,7 +1168,8 @@ def unicodify(
     error: str = "replace",
     strip_null: bool = False,
     log_exception: bool = True,
-) -> str: ...
+) -> str:
+    ...
 
 
 def unicodify(