Current best hparams for local 1d.

def img2img_transformer_b3():
  """Current best hparams for local 1d."""
  hparams = img2img_transformer_base()
  hparams.batch_size = 2
  hparams.layer_preprocess_sequence = "none"
  hparams.layer_postprocess_sequence = "dan"
  hparams.block_length = 128
  hparams.sampling_temp = 0.9
  return hparams