code: def test_forward_no_cast_grad(self):
      # This test would fail if F.cast does not create new function nodes for
      # no-op casts
      x = chainer.Variable(self.x)
      y1 = functions.cast(x, self.dtype)
      y2 = functions.cast(x, self.dtype)
      z = y1 + y2
      gy1, gy2 = chainer.grad([z], [y1, y2], [numpy.ones_like(z.data)])
      assert gy1.dtype == self.dtype
      assert gy2.dtype == self.dtype
      numpy.testing.assert_array_equal(
          gy1.data, numpy.ones_like(y1.data)
      )
      numpy.testing.assert_array_equal(
          gy2.data, numpy.ones_like(y2.data)
      )
  
imports: import unittest
  import numpy
  import chainer
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  import chainerx
label_desc: Use image node_id 5 for calling the TestNoCast obj's underlying member method code with example usage: obj.test_forward_no_cast_grad() without return types