code: def list_metrics(self, project, page_size=0, page_token=None):
          
          path = "projects/%s" % (project,)
          page_iter = self._gapic_api.list_log_metrics(path, page_size=page_size)
          page_iter.client = self._client
          page_iter.next_page_token = page_token
          page_iter.item_to_value = _item_to_metric
          return page_iter
docs: List metrics for the project associated with this client.
  
          :type project: str
          :param project: ID of the project whose metrics are to be listed.
  
          :type page_size: int
          :param page_size: maximum number of metrics to return, If not passed,
                            defaults to a value set by the API.
  
          :type page_token: str
          :param page_token: opaque marker for the next "page" of metrics. If not
                             passed, the API will return the first page of
                             metrics.
  
          :rtype: :class:`~google.api_core.page_iterator.Iterator`
          :returns: Iterator of
                    :class:`~google.cloud.logging.metric.Metric`
                    accessible to the current API.