import tensorflow as tf


    with tf.control_dependencies([train_op]), tf.name_scope('ema'):
        ema = tf.train.ExponentialMovingAverage(decay=MOVING_AVERAGE_DECAY, num_updates=global_step)
        train_op = ema.apply(tf.trainable_variables())

    return tf.estimator.EstimatorSpec(mode, loss=total_loss, train_op=train_op)


def add_weight_decay(weight_decay):
    """Add L2 regularization to all (or some) trainable kernel weights."""
