def bulk_update(cls, files, api=None):
        """
        This call updates the details for multiple specified files.
        Use this call to set new information for the files, thus replacing
        all existing information and erasing omitted parameters. For each
        of the specified files, the call sets a new name, new tags and
        metadata.
        :param files: List of file instances.
        :param api: Api instance.
        :return: List of FileBulkRecord objects.
        """
        if not files:
            raise SbgError('Files are required.')

        api = api or cls._API
        data = {
            'items': [
                {
                    'id': file_.id,
                    'name': file_.name,
                    'tags': file_.tags,
                    'metadata': file_.metadata,
                }
                for file_ in files
            ]
        }

        logger.info('Updating files in bulk.')
        response = api.post(url=cls._URL['bulk_update'], data=data)
        return FileBulkRecord.parse_records(response=response, api=api)