import tensorflow as tf

            # state, target and action
            self.state = tf.placeholder(tf.float32, [None,num_state], name="state")
            self.target = tf.placeholder(tf.float32,[None,1], name="target")
            self.a_his = tf.placeholder(tf.float32, [None, num_action], name="action_hist")        
            
            # layers
