import tensorflow as tf


    with tf.variable_scope("loss", reuse=reuse):
        # set up placeholders
        act_t_ph = tf.placeholder(tf.int32, [None], name="action")
        rew_t_ph = tf.placeholder(tf.float32, [None], name="reward")
        done_mask_ph = tf.placeholder(tf.float32, [None], name="done")
