code: def test_double_plus(self):
      self._dll.tf_bd.restype = c_double
      self._dll.tf_bd.argtypes = (c_byte, c_double)
      self.assertEqual(self._dll.tf_bd(0, 42.0), 14.0)
      self.assertEqual(self.S(), 42)
  
imports: import unittest
  from ctypes import *
  from ctypes.test import need_symbol
  import _ctypes_test
label_desc: Use image node_id 26 for calling the CFunctions obj's underlying member method code with example usage: obj.test_double_plus() without return types