Returns iterator over files within archive.

    **Important Note**: caller should read files as they are yielded.
    Reading out of order is slow.

    Args:
      resource: path to archive or `tfds.download.Resource`.

    Returns:
      Generator yielding tuple (path_within_archive, file_obj).

def iter_archive(self, resource):
    """Returns iterator over files within archive.

    **Important Note**: caller should read files as they are yielded.
    Reading out of order is slow.

    Args:
      resource: path to archive or `tfds.download.Resource`.

    Returns:
      Generator yielding tuple (path_within_archive, file_obj).
    """
    if isinstance(resource, six.string_types):
      resource = resource_lib.Resource(path=resource)
    return extractor.iter_archive(resource.path, resource.extract_method)