class_docstr: Test AssertFunction layer.
class_docstr_tok: ["Test","AssertFunction","layer","."]
code: def test_multi_output_rank_fail(self):
      layer = tl.AssertFunction(
          "...34->...x,...y",
          tl.Branch(
              tl.Flatten(n_axes_to_keep=3),
              tl.Serial(),
          ),
      )
      x = np.ones((1, 2, 3, 4))
      with self.assertRaises(tl.LayerError):
          layer(x)
  
imports: from absl.testing import absltest
  import numpy
  import trax.layers
label_desc: Use image node_id 11 for calling the AssertFunctionTest obj's underlying member method code with example usage: obj.test_multi_output_rank_fail() without return types