code: def check_forward_valid_none(self, *inputs_data):
      inputs_variable = [
          chainer.Variable(v) if v is not None else v
          for v in inputs_data
      ]
      xp = self.link.xp
      inputs_data = [
          xp.zeros(self.h_prevs[0].shape, dtype=self.dtype)
          if v is None
          else v
          for v in inputs_data[:-1]
      ] + [
          xp.zeros(self.x.shape, dtype=self.dtype)
          if inputs_data[-1] is None
          else inputs_data[-1]
      ]
  
      if self.n_ary == 0:
          # in this case for link(x) without cs and hs,
          # it does not include any None.
          pass
      else:
          c, h = self.link(*inputs_variable)
          self.assertEqual(c.data.dtype, self.dtype)
          self.assertEqual(h.data.dtype, self.dtype)
  
          # Compute expected out
          if self.model_type == "ChildSumTreeLSTM":
              c_expect, h_expect = _child_sum_tree_lstm(
                  self.link, *inputs_data
              )
          elif self.model_type == "NaryTreeLSTM":
              c_expect, h_expect = _nary_tree_lstm(
                  self.link, *inputs_data
              )
          else:
              NotImplementedError()
  
          testing.assert_allclose(
              c_expect, c.data, **self.check_forward_options
          )
          testing.assert_allclose(
              h_expect, h.data, **self.check_forward_options
          )
  
imports: import unittest
  import numpy
  import chainer
  from chainer import backend
  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 6 for calling the TestTreeLSTM obj's underlying member method code with example usage: obj.check_forward_valid_none() without return types