code: def test_walk_dfs():
      relu = Relu(5)
      relu2 = Relu(5)
      inner_chain = chain(relu, relu2)
      chained = chain(inner_chain, inner_chain)
      assert list(chained.walk(order="dfs_pre")) == [
          chained,
          inner_chain,
          relu,
          relu2,
      ]
      assert list(chained.walk(order="dfs_post")) == [
          relu,
          relu2,
          inner_chain,
          chained,
      ]
  
imports: import threading
  import time
  from collections import Counter
  import numpy
  import pytest
  from thinc.api import Adam, CupyOps, Dropout, Linear, Model, Relu, Shim, Softmax, chain, change_attr_values, concatenate, set_dropout_rate, use_ops, with_debug, wrap_model_recursive
  from thinc.compat import has_cupy_gpu
  from ..util import make_tempdir
label_desc: Use image node_id 32 for calling a global function with example usage: test_walk_dfs() without return types