code: def assertNone(expr, message=None):
      
      if expr is not None:
          raise TestStepFail(
              format_message(message) if message is not None else "Assert: %s != None" % str(expr))
docs: Assert that expr is None.
  
      :param expr: expression.
      :param message: Message set to raised Exception
      :raises: TestStepFail if expr is not None.