def METHOD_NAME(bucket_name: str, dir_name: str) -> List[storage.blob.Blob]:
    """Lists all files in a directory.
    Args:
        bucket_name: str. The name of the GCS bucket.
        dir_name: str. The directory whose files should be listed. This
            should not start with '/'.
    Returns:
        list(Blob). A list of blobs.
    """
    return list(
        _get_client().list_blobs(_get_bucket(bucket_name), prefix=dir_name))