'Beam search decoding.
Args:
model: The seq2seq attentional model.
batch_reader: The batch data reader.
hps: Hyperparamters.
vocab: Vocabulary'

def __init__(self, model, batch_reader, hps, vocab):

    self._model = model
    self._model.build_graph()
    self._batch_reader = batch_reader
    self._hps = hps
    self._vocab = vocab
    self._saver = tf.train.Saver()
    self._decode_io = DecodeIO(FLAGS.decode_dir)
