Best config for 2.90 bits/dim on CIFAR10 using DMOL.

def imagetransformer_cifar10_base_dmol():
  """Best config for 2.90 bits/dim on CIFAR10 using DMOL."""
  hparams = image_transformer_base()
  hparams.likelihood = cia.DistributionType.DMOL
  hparams.num_channels = 1
  hparams.bottom["targets"] = modalities.image_channel_compress_targets_bottom
  hparams.top["targets"] = modalities.identity_top
  hparams.num_heads = 8
  hparams.batch_size = 8
  hparams.sampling_method = "random"
  hparams.layer_preprocess_sequence = "n"
  hparams.layer_postprocess_sequence = "da"
  hparams.summarize_grads = True
  hparams.hidden_size = 256
  hparams.filter_size = 512
  hparams.attention_key_channels = 512
  hparams.attention_value_channels = 512
  hparams.num_decoder_layers = 12
  hparams.layer_prepostprocess_dropout = 0.1
  hparams.learning_rate = 0.1
  hparams.layer_preprocess_sequence = "none"
  hparams.layer_postprocess_sequence = "dan"
  hparams.pos = "emb"
  hparams.unconditional = True
  return hparams