code: def test_reversible_swap(self, backend):
      with fastmath.use_backend(backend):
          layer = tl.ReversibleSwap()
          xs = [np.array([1, 2]), np.array([10, 20])]
          ys = layer(xs)
          self.assertEqual(tl.to_list(ys), [[10, 20], [1, 2]])
  
imports: from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from trax import fastmath
  import trax.layers
label_desc: Use image node_id 1 for calling the ReversibleLayerTest obj's underlying member method code with example usage: obj.test_reversible_swap(backend) without return types