Get's the tensors representing the attentions from a build model.

  The attentions are stored in a dict on the Transformer object while building
  the graph.

  Args:
    translate_model: Transformer object to fetch the attention weights from.

  Returns:
  Tuple of attention matrices; (
      enc_atts: Encoder self attention weights.
        A list of `num_layers` numpy arrays of size
        (batch_size, num_heads, inp_len, inp_len)
      dec_atts: Decoder self attetnion weights.
        A list of `num_layers` numpy arrays of size
        (batch_size, num_heads, out_len, out_len)
      encdec_atts: Encoder-Decoder attention weights.
        A list of `num_layers` numpy arrays of size
        (batch_size, num_heads, out_len, inp_len)
  )

def get_att_mats(translate_model):
  """Get's the tensors representing the attentions from a build model.

  The attentions are stored in a dict on the Transformer object while building
  the graph.

  Args:
    translate_model: Transformer object to fetch the attention weights from.

  Returns:
  Tuple of attention matrices; (
      enc_atts: Encoder self attention weights.
        A list of `num_layers` numpy arrays of size
        (batch_size, num_heads, inp_len, inp_len)
      dec_atts: Decoder self attetnion weights.
        A list of `num_layers` numpy arrays of size
        (batch_size, num_heads, out_len, out_len)
      encdec_atts: Encoder-Decoder attention weights.
        A list of `num_layers` numpy arrays of size
        (batch_size, num_heads, out_len, inp_len)
  )
  """
  enc_atts = []
  dec_atts = []
  encdec_atts = []

  prefix = "transformer/body/"
  postfix_self_attention = "/multihead_attention/dot_product_attention"
  if translate_model.hparams.self_attention_type == "dot_product_relative":
    postfix_self_attention = ("/multihead_attention/"
                              "dot_product_attention_relative")
  postfix_encdec = "/multihead_attention/dot_product_attention"

  for i in range(translate_model.hparams.num_hidden_layers):
    enc_att = translate_model.attention_weights[
        "%sencoder/layer_%i/self_attention%s"
        % (prefix, i, postfix_self_attention)]
    dec_att = translate_model.attention_weights[
        "%sdecoder/layer_%i/self_attention%s"
        % (prefix, i, postfix_self_attention)]
    encdec_att = translate_model.attention_weights[
        "%sdecoder/layer_%i/encdec_attention%s" % (prefix, i, postfix_encdec)]
    enc_atts.append(enc_att)
    dec_atts.append(dec_att)
    encdec_atts.append(encdec_att)

  return enc_atts, dec_atts, encdec_atts