code: def update(self):
          
          api = self._client.instance_admin_api
          instance_pb = admin_v1_pb2.Instance(
              name=self.name,
              config=self.configuration_name,
              display_name=self.display_name,
              node_count=self.node_count,
          )
          field_mask = FieldMask(paths=["config", "display_name", "node_count"])
          metadata = _metadata_with_prefix(self.name)
  
          future = api.update_instance(
              instance=instance_pb, field_mask=field_mask, metadata=metadata
          )
  
          return future
docs: Update this instance.
  
          See
          https://cloud.google.com/spanner/reference/rpc/google.spanner.admin.instance.v1#google.spanner.admin.instance.v1.InstanceAdmin.UpdateInstance
  
          .. note::
  
             Updates the ``display_name`` and ``node_count``. To change those
             values before updating, set them via
  
             .. code:: python
  
                instance.display_name = 'New display name'
                instance.node_count = 5
  
              before calling :meth:`update`.
  
          :rtype: :class:`google.api_core.operation.Operation`
          :returns: an operation instance
          :raises NotFound: if the instance does not exist