import tensorflow as tf

                    vs[0].graph.colocate_with(vs[0]):
                counter = tf.Variable(
                    0, name="counter", trainable=False, dtype=tf.int32)

        with tf.name_scope('AccumGradOptimizer'):
            ops = []
            for s, gv in zip(slots, grads_and_vars):
                g, v = gv
