code: def forward(self, inputs, device):
      x1, x2 = inputs
      y = F.matmul(x1, x2, transa=self.transa, transb=self.transb)
      return (y,)
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backend import CpuDevice
  import chainer.functions
  from chainer import testing
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the TestMatMul obj's underlying member method code with example usage: obj.forward(inputs, device) and returns: y