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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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