Initialize the defined network and restore from files is so specified.

def _initialize_model(self):
        """ Initialize the defined network and restore from files is so specified. """
        # Initialize all variables first
        self.sess.run(tf.local_variables_initializer())
        self.sess.run(tf.global_variables_initializer())
        if self.flags['RESTORE_META'] == 1:
            print('Restoring from .meta file')
            self._restore_meta()
        elif self.flags['RESTORE_SLIM'] == 1:
            print('Restoring TF-Slim Model.')
            all_model_variables = tf.global_variables()
            self._restore_slim(all_model_variables)
        else:
            print("Model training from scratch.")