code: def get_log_rhos(target_action_log_probs, behaviour_action_log_probs):
      
      t = tf.stack(target_action_log_probs)
      b = tf.stack(behaviour_action_log_probs)
      log_rhos = tf.reduce_sum(t - b, axis=0)
      return log_rhos
docs: With the selected log_probs for multi-discrete actions of behaviour
      and target policies we compute the log_rhos for calculating the vtrace.