code: def register_metric_descriptor(self, oc_md):
          
          metric_type = self.get_metric_type(oc_md)
          with self._md_lock:
              if metric_type in self._md_cache:
                  return self._md_cache[metric_type]
  
          descriptor = self.get_metric_descriptor(oc_md)
          project_name = self.client.project_path(self.options.project_id)
          sd_md = self.client.create_metric_descriptor(project_name, descriptor)
          with self._md_lock:
              self._md_cache[metric_type] = sd_md
          return sd_md
docs: Register a metric descriptor with stackdriver.