import tensorflow as tf

            used_mean /= (1. - bn_lag**(step + 1))
            used_var -= (1 - bn_lag) * (used_var - tf.stop_gradient(var))
            used_var /= (1. - bn_lag**(step + 1))
    else:
        used_mean, used_var = mean, var
        cur_mean, cur_var = used_mean, used_var

    # update variables
    if train:
        with tf.name_scope(name, "AssignMovingAvg", [mean, cur_mean, decay]):
            with ops.colocate_with(mean):
                new_mean = tf.assign_sub(
                    mean,
                    tf.check_numerics(
                        decay * (mean - cur_mean), "NaN in moving mean."))
        with tf.name_scope(name, "AssignMovingAvg", [var, cur_var, decay]):
            with ops.colocate_with(var):
                new_var = tf.assign_sub(
