def get_local_file_name(cur_key):
    """
    Return the local file name for a given cost usage report key.

    If an assemblyID is present in the key, it will prepend it to the filename.

    Args:
        cur_key (String): reportKey value from manifest file.
        example:
        With AssemblyID: /koku/20180701-20180801/882083b7-ea62-4aab-aa6a-f0d08d65ee2b/koku-1.csv.gz
        Without AssemblyID: /koku/20180701-20180801/koku-Manifest.json

    Returns:
        (String): file name for the local file,
                example:
                With AssemblyID: "882083b7-ea62-4aab-aa6a-f0d08d65ee2b-koku-1.csv.gz"
                Without AssemblyID: "koku-Manifest.json"

    """
    local_file_name = cur_key.split("/")[-1]

    return local_file_name