code: def list_instances(self):
          
          resp = self.instance_admin_client.list_instances(self.project_path)
          instances = [Instance.from_pb(instance, self) for instance in resp.instances]
          return instances, resp.failed_locations
docs: List instances owned by the project.
  
          For example:
  
          .. literalinclude:: snippets.py
              :start-after: [START bigtable_list_instances]
              :end-before: [END bigtable_list_instances]
  
          :rtype: tuple
          :returns:
              (instances, failed_locations), where 'instances' is list of
              :class:`google.cloud.bigtable.instance.Instance`, and
              'failed_locations' is a list of locations which could not
              be resolved.