code: def set(self, project, date, data, data_ts):
          
          data['cache_metadata'] = {
              'project': project,
              'date': date.strftime('%Y%m%d'),
              'updated': time.time(),
              'version': VERSION,
              'data_ts': data_ts
          }
          fpath = self._path_for_file(project, date)
          logger.debug('Cache SET project=%s date=%s - path=%s',
                       project, date.strftime('%Y-%m-%d'), fpath)
          with open(fpath, 'w') as fh:
              fh.write(json.dumps(data))
docs: Set the cache data for a specified project for the specified date.
  
          :param project: project name to set data for
          :type project: str
          :param date: date to set data for
          :type date: datetime.datetime
          :param data: data to cache
          :type data: dict
          :param data_ts: maximum timestamp in the BigQuery data table
          :type data_ts: int