Creates a list of files in a directory that have the provided extensions.

    :param dir: String path of directory containing files to be listed
    :param exts: Variable amount of string arguments specifying the
        extensions to be used. If none are provided, will default to finding
        every file in the directory
    :return: A list of string paths to each desired file in the directory.

def get_files_in_dir(dir, *exts):
    """
    Creates a list of files in a directory that have the provided extensions.

    :param dir: String path of directory containing files to be listed
    :param exts: Variable amount of string arguments specifying the
        extensions to be used. If none are provided, will default to finding
        every file in the directory
    :return: A list of string paths to each desired file in the directory.
    """
    file_paths = []
    if exts is None:
        exts = ['']
    for ext in exts:
        file_paths.extend(glob.glob(dir + '*' + ext))
    return file_paths