Helper for log metric-related API calls.

        See
        https://cloud.google.com/logging/docs/reference/v2/rest/v2/projects.metrics

def metrics_api(self):
        """Helper for log metric-related API calls.

        See
        https://cloud.google.com/logging/docs/reference/v2/rest/v2/projects.metrics
        """
        if self._metrics_api is None:
            if self._use_grpc:
                self._metrics_api = _gapic.make_metrics_api(self)
            else:
                self._metrics_api = JSONMetricsAPI(self)
        return self._metrics_api