code: def test_forward_no_cast_variable(self):
      # If backprop is disabled, it's safe to simply return the input
      # variable for no-op casts.
      x = chainer.Variable(self.x)
      with chainer.using_config("enable_backprop", False):
          y = functions.cast(x, self.dtype)
      assert y is x
  
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 4 for calling the TestNoCast obj's underlying member method code with example usage: obj.test_forward_no_cast_variable() without return types