code: def test_simple(self):
      tree = links.BinaryHierarchicalSoftmax.create_huffman_tree(
          {"x": 8, "y": 6, "z": 5, "w": 4, "v": 3}
      )
      expect = (("z", "y"), (("v", "w"), "x"))
      self.assertEqual(expect, tree)
  
imports: import copy
  import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import gradient_check
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import condition
label_desc: Use image node_id 2 for calling the TestHuffmanTree obj's underlying member method code with example usage: obj.test_simple() without return types