Ordered discrete autoencoder model.

def autoencoder_ordered_discrete_image64():
  """Ordered discrete autoencoder model."""
  hparams = autoencoder_ordered_discrete()
  hparams.batch_size = 32
  hparams.num_hidden_layers = 6
  hparams.bottleneck_warmup_steps *= 2
  hparams.gan_codes_warmup_steps *= 2

  return hparams