'Called right before the first iteration. The main difference to
`setup_graph` is that at this point the graph is finalized and a default session is initialized.
Override this method to, e.g. run some operations under the session.
This is similar to ``tf.train.SessionRunHook.after_create_session()``, but different:
it is called after the session is initialized by :class:`tfutils.SessionInit`.'

def _before_train(self):

    pass
