def test_type(self):
        rset = event.ResultSet()
        with pytest.raises(NotImplementedError):
            rset.extend([])
        with pytest.raises(NotImplementedError):
            rset.extend(False)
def __init__(self, gan=None, config=None, trainer=None):
      super().__init__(config=config, gan=gan, trainer=trainer)
      self.d_grads = None
      self.g_grads = None