import tensorflow as tf

            ch_emb = tf.reduce_max(ch_emb, axis = 1)
            qh_emb = tf.reduce_max(qh_emb, axis = 1)

            ch_emb = tf.reshape(ch_emb, [N, PL, ch_emb.shape[-1]])
            qh_emb = tf.reshape(qh_emb, [N, QL, ch_emb.shape[-1]])

