diff --git a/hpc_helper/_exceptions.py b/hpc_helper/_exceptions.py
deleted file mode 100644
index f674361..0000000
--- a/hpc_helper/_exceptions.py
+++ /dev/null
@@ -1,7 +0,0 @@
-"""A set of custom exceptions."""
-
-__all__ = ["FileExtensionError"]
-
-
-class FileExtensionError(Exception):
-    """An error indicating that the file name has the wrong file extension."""
diff --git a/hpc_helper/_utils.py b/hpc_helper/_utils.py
deleted file mode 100644
index e093884..0000000
--- a/hpc_helper/_utils.py
+++ /dev/null
@@ -1,46 +0,0 @@
-"""Some utils functions for this package."""
-from pathlib import Path
-from typing import Optional, Sequence, Union
-
-from hpc_helper._exceptions import FileExtensionError
-from hpc_helper._types import path_t
-
-
-def _assert_file_extension(
-    file_name: path_t, expected_extension: Union[str, Sequence[str]], raise_exception: Optional[bool] = True
-) -> Optional[bool]:
-    """Check if a file has the correct file extension.
-
-    Parameters
-    ----------
-    file_name : path or str
-        file name to check for correct extension
-    expected_extension : str or list of str
-        file extension (or a list of file extensions) to check for
-    raise_exception : bool, optional
-        whether to raise an exception or return a bool value
-
-    Returns
-    -------
-    ``True`` if ``file_name`` ends with one of the specified file extensions, ``False`` otherwise
-    (if ``raise_exception`` is ``False``)
-
-    Raises
-    ------
-    :exc:`~biopsykit.exceptions.FileExtensionError`
-        if ``raise_exception`` is ``True`` and ``file_name`` does not end with any of the specified
-        ``expected_extension``
-
-    """
-    # ensure pathlib
-    file_name = Path(file_name)
-    if isinstance(expected_extension, str):
-        expected_extension = [expected_extension]
-    if file_name.suffix not in expected_extension:
-        if raise_exception:
-            raise FileExtensionError(
-                "The file name extension is expected to be one of {}. "
-                "Instead it has the following extension: {}".format(expected_extension, file_name.suffix)
-            )
-        return False
-    return True