'Inputs to be fed to the graph.'

def _add_placeholders(self):

    hps = self._hps
    self._articles = tf.placeholder(tf.int32, [hps.batch_size, hps.enc_timesteps], name='articles')
    self._abstracts = tf.placeholder(tf.int32, [hps.batch_size, hps.dec_timesteps], name='abstracts')
    self._targets = tf.placeholder(tf.int32, [hps.batch_size, hps.dec_timesteps], name='targets')
    self._article_lens = tf.placeholder(tf.int32, [hps.batch_size], name='article_lens')
    self._abstract_lens = tf.placeholder(tf.int32, [hps.batch_size], name='abstract_lens')
    self._loss_weights = tf.placeholder(tf.float32, [hps.batch_size, hps.dec_timesteps], name='loss_weights')
