code: def cache(self):
      
      if not self._bucket_width or self._untrusted_time is None:
        raise ValueError('QueryCompute must be initialized with a bucket_width '
                         'and an untrusted_time in order to write to the cache.')
  
      now = datetime.datetime.now()
      untrusted_time = now - datetime.timedelta(seconds=self._untrusted_time)
      list(self._query_cache.compute_and_cache_missing_buckets(
          self._start_time,
          self._end_time,
          untrusted_time))
docs: Call a user defined query and cache the results