@staticmethod
def sort_key(format):
    """ Get a key to sort a format

        Args:
            format (:obj:`Format`): format

        Returns:
            :obj:`tuple`
        """
    return (format.id, format.name, format.version, format.edam_id, format.
        url, format.spec_url, format.mime_type, format.extension, format.
        sed_urn)
