The slicenet model, main step used for training.

def slicenet_internal(inputs, targets, target_space, hparams, run_decoder=True):
  """The slicenet model, main step used for training."""
  with tf.variable_scope("slicenet"):
    # Project to hidden size if necessary
    if inputs.get_shape().as_list()[-1] != hparams.hidden_size:
      inputs = common_layers.conv_block(
          inputs,
          hparams.hidden_size, [((1, 1), (3, 3))],
          first_relu=False,
          padding="SAME",
          force2d=True)

    # Flatten inputs and encode.
    inputs = tf.expand_dims(common_layers.flatten4d3d(inputs), axis=2)
    inputs_mask = 1.0 - embedding_to_padding(inputs)
    inputs = common_layers.add_timing_signal(inputs)  # Add position info.
    target_space_emb = embed_target_space(target_space, hparams.hidden_size)
    extra_layers = int(hparams.num_hidden_layers * 1.5)
    inputs_encoded = multi_conv_res(
        inputs, "SAME", "encoder", extra_layers, hparams, mask=inputs_mask)
    if not run_decoder:
      return inputs_encoded
    # Do the middle part.
    decoder_start, similarity_loss = slicenet_middle(
        inputs_encoded, targets, target_space_emb, inputs_mask, hparams)
    # Decode.
    decoder_final = multi_conv_res(
        decoder_start,
        "LEFT",
        "decoder",
        hparams.num_hidden_layers,
        hparams,
        mask=inputs_mask,
        source=inputs_encoded)
    return decoder_final, tf.reduce_mean(similarity_loss)