code: def forward(self, inputs, device):
      (x,) = inputs
      return (functions.batch_inv(x),)
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils import type_check
label_desc: Use image node_id 3 for calling the BatchInvFunctionTest obj's underlying member method code with example usage: obj.forward(inputs, device) and returns: functions