为什么不能将赋值操作作为参数添加到tensorflow中的控件相关性中?

我有一个简单的模型。但是我需要在执行更新之前修改一个变量。因此,我有以下几点:

l = tf.Variable(tf.constant(0.01), trainable=False, name="l")
baseline = tf.Variable(tf.constant(0.0), dtype=tf.float32, name="baseline")

# Actor optimizer
# Note that our target is: e^{-L} where L is the loss on the validation dataset. 
# So we pass to the target mae_loss in the code below
def optimize_actor(scores_a, scores_v, target):
    with tf.name_scope('Actor_Optimizer'):
        update_moving_loss = tf.assign(baseline, l * baseline + (1 - l) * target, name="update_baseline")
        dec_l = l.assign_add(0.001)

        update_ops = tf.get_collection(tf.GraphKeys.UPDATE_OPS)
        with tf.control_dependencies([update_ops, update_moving_loss, dec_l]):
            loss_a = scores_a * tf.exp(target - baseline)
            loss_v = scores_v * tf.exp(target - baseline)
            actor_a_optimizer = tf.train.AdamOptimizer(0.0001).minimize(loss_a)
            actor_v_optimizer = tf.train.AdamOptimizer(0.0001).minimize(loss_v)
    return actor_a_optimizer, actor_v_optimizer

因此,在运行上述脚本时,我出现以下错误:

Can not convert a list into a Tensor or Operation.

导致此问题的原因是 update_moving_loss 和 dec_l 。当我删除它们时,代码运行良好。

请注意,我使用的是tensorflow 1.7

非常感谢您的帮助!!!