def notify(self, method_name, **cb_kwargs):
        """Call the callback method specified in ``method_name`` with
        parameters specified in ``cb_kwargs``.

        Method names can be one of:
        * on_train_begin
        * on_train_end
        * on_epoch_begin
        * on_epoch_end
        * on_batch_begin
        * on_batch_end

        """
        getattr(self, method_name)(self, **cb_kwargs)
        for _, cb in self.callbacks_:
            getattr(cb, method_name)(self, **cb_kwargs)