import tensorflow as tf


        # the word embeddings
        with tf.device("/cpu:0"):
            self.embedding_weights = tf.get_variable(
                "embedding", [self._n_tokens_vocab, projection_dim],
                dtype=DTYPE,
            )
            self.embedding = tf.nn.embedding_lookup(self.embedding_weights,
                                                self.ids_placeholder)


    def _build_lstms(self):
        # now the LSTMs
        # these will collect the initial states for the forward
