code: def test_dot_product_causal_attention_fast_inference(self):
      model_fn = functools.partial(
          transformer.TransformerLM,
          d_model=4,
          d_ff=8,
          n_layers=2,
          n_heads=2,
      )
      test_utils.test_eval_equals_predict_discrete(model_fn)
  
file_path: trax/trax/models/transformer_test.py
imports: import functools
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from trax import fastmath
  from trax import shapes
  from trax.layers import test_utils
  from trax.models import transformer
label_desc: Use image node_id 4 for calling the TransformerTest obj's underlying member method code with example usage: obj.test_dot_product_causal_attention_fast_inference() without return types