'save.
Save a Tensorflow model
Arguments:
model_file: `str`. Saving path of tensorflow model
global_step: `int`. The training step to append to the
model file name (optional).'

def save(self, model_file, global_step=None):

    obj_lists = utils.fix_saver()
    if (not os.path.isabs(model_file)):
        model_file = os.path.abspath(os.path.join(os.getcwd(), model_file))
    self.saver.save(self.session, model_file, global_step=global_step)
    utils.fix_saver(obj_lists)
