code: def test_tree_fn(self):
      def add(x, y):
          return x + y
  
      tree_add = tree_util.tree_fn(add)
      tree_x = [1, 2, 3]
      tree_y = [1, 10, 100]
      output = tree_add(tree_x, tree_y)
      exp_output = [2, 12, 103]
      # Test output.
      np.testing.assert_allclose(output, exp_output)
  
file_path: rlax/rlax/_src/tree_util_test.py
imports: from absl.testing import absltest
  import chex
  import jax
  import jax.numpy
  import numpy
  from rlax._src import tree_util
label_desc: Use image node_id 8 for calling the TreeUtilTest obj's underlying member method code with example usage: obj.test_tree_fn() and returns: unknown