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.

def list_instances(self):
        """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.
        """
        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