Big model.

def vqa_self_attention_feature_batch1024_big():
  """Big model."""
  hparams = vqa_self_attention_feature_batch1024()
  hparams.learning_rate_constant = 7e-4
  hparams.batch_size = 256
  hparams.hidden_size = 1024
  hparams.filter_size = 4096
  hparams.num_heads = 16
  hparams.layer_prepostprocess_dropout = 0.3
  hparams.attention_dropout = 0.3
  hparams.relu_dropout = 0.3
  return hparams