separate rgb embeddings.

def imagetransformer_sep_channels_16l_16h_imgnet_lrg_loc_128():
  """separate rgb embeddings."""
  hparams = imagetransformer_sep_channels_12l_16h_imagenet_large()
  hparams.num_hidden_layers = 16
  hparams.local_attention = True
  hparams.batch_size = 1
  hparams.block_length = 128
  return hparams