'Defines what to do in one iteration. The default is:
``self.hooked_sess.run(self.train_op)``.
The behavior can be changed by either defining what is ``train_op``,
or overriding this method.'

def run_step(self):

    if (not hasattr(self, 'train_op')):
        raise NotImplementedError('Please    either    set    `Trainer.train_op`    or    provide    an    implementation    of    Trainer.run_step()!')
    self.hooked_sess.run(self.train_op)
