code: def forward_expected(self, inputs):
      x, t = inputs
      count = 0
      correct = 0
      x_flatten = x.ravel()
      t_flatten = t.ravel()
      for i in six.moves.range(t_flatten.size):
          if t_flatten[i] == -1:
              continue
          pred = int(x_flatten[i] >= 0)
          if pred == t_flatten[i]:
              correct += 1
          count += 1
      expected = float(correct) / count
      expected = force_array(expected, self.dtype)
      return (expected,)
  
imports: import unittest
  import numpy
  import six
  import chainer
  from chainer import functions
  from chainer import testing
  from chainer.utils import force_array
  from chainer.utils import type_check
label_desc: Use image node_id 4 for calling the TestBinaryAccuracy obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: expected