code: def list_clusters(self):
          
          resp = self._client.instance_admin_client.list_clusters(self.name)
          clusters = [Cluster.from_pb(cluster, self) for cluster in resp.clusters]
          return clusters, resp.failed_locations
docs: List the clusters in this instance.
  
          For example:
  
          .. literalinclude:: snippets.py
              :start-after: [START bigtable_list_clusters_on_instance]
              :end-before: [END bigtable_list_clusters_on_instance]
  
          :rtype: tuple
          :returns:
              (clusters, failed_locations), where 'clusters' is list of
              :class:`google.cloud.bigtable.instance.Cluster`, and
              'failed_locations' is a list of locations which could not
              be resolved.