code: def test_rnnlm_forward_shape(self, backend):
      with fastmath.use_backend(backend):
          model = rnn.RNNLM(vocab_size=20, d_model=16)
          x = np.ones((3, 28)).astype(np.int32)
          _, _ = model.init(shapes.signature(x))
          y = model(x)
          self.assertEqual(y.shape, (3, 28, 20))
  
file_path: trax/trax/models/rnn_test.py
imports: from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from trax import fastmath
  from trax import shapes
  from trax.models import rnn
label_desc: Use image node_id 1 for calling the RNNTest obj's underlying member method code with example usage: obj.test_rnnlm_forward_shape(backend) without return types