[docs] def train(self, mode=True):
  r"""Sets the module in training mode.

  This has any effect only on certain modules. See documentations of
  particular modules for details of their behaviors in training/evaluation
  mode, if they are affected, e.g. :class:`Dropout`, :class:`BatchNorm`,
  etc.

  Returns:
   Module: self
  """
  self.training = mode
  for module in self.children():
   module.train(mode)
  return self

[docs] def eval(self):
  r"""Sets the module in evaluation mode.

  This has any effect only on certain modules. See documentations of
  particular modules for details of their behaviors in training/evaluation
  mode, if they are affected, e.g. :class:`Dropout`, :class:`BatchNorm`,
  etc.
  """
  #该方法调用了nn.train()方法，把参数默认值改为false. 增加聚合性
  return self.train(False)