code: def forward_expected(self, inputs):
      (x,) = inputs
      return (x.flatten(),)
  
file_path: chainer/tests/chainer_tests/functions_tests/array_tests/test_flatten.py
imports: import numpy
  from chainer import functions
  from chainer import testing
label_desc: Use image node_id 2 for calling the TestFlatten obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: x