def get_main_type_mock(path):
    """Detect audio or video type from file extension.

    Used to mock real method which needs actual files to be present.

    Args:
        path (path.Path): Path to a file.

    Returns:
        str: "video" if file extension is "mp4" or "mkv",
        "audio" if file extension is "ogg" or "flac",
        None otherwise.
    """
    ext = path.ext

    if ext in [".mp4", ".mkv"]:
        return "video"
    if ext in [".ogg", ".flac"]:
        return "audio"

    return None