big 1d model for conditional image generation.

def imagetransformer_bas8l_8h_big_uncond_dr03_imgnet():
  """big 1d model for conditional image generation."""
  hparams = imagetransformer_base_14l_8h_big_dr01()
  # num_hidden_layers
  hparams.num_decoder_layers = 8
  hparams.num_heads = 8
  hparams.hidden_size = 512
  hparams.filter_size = 2048
  hparams.layer_prepostprocess_dropout = 0.3
  return hparams