code: def forward_expected(self, inputs):
      x, t = inputs
      expected = r2_score(
          x,
          t,
          sample_weight=self.sample_weight,
          multioutput=self.multioutput,
      )
      expected = force_array(expected, self.dtype)
      return (expected,)
  
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 force_array
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the TestAccuracy obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: expected