code: def test_sru(self, backend):
      with fastmath.use_backend(backend):
          layer = tl.SRU(7)
          x = np.ones((8, 9, 7), np.float32)
          _, _ = layer.init(shapes.signature(x))
          y = layer(x)
          self.assertEqual(y.shape, x.shape)
  
file_path: trax/trax/layers/rnn_test.py
imports: from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from trax import fastmath
  from trax import shapes
  import trax.layers
label_desc: Use image node_id 4 for calling the RnnTest obj's underlying member method code with example usage: obj.test_sru(backend) without return types