def __call__ self cls if self preferences is not None for field_name p

    def __call__(self, cls):
        if self.preferences is not None:
            for field_name, pref_factory in self.preferences:
                template_methods = inspect.getmembers(self.__class__, inspect.isfunction)

                for name, tempalte_method in template_methods:
                    if name.startswith('template_'):
                        test_method_name_template, test_method = tempalte_method(field_name, pref_factory)
                        test_method_name = test_method_name_template % {'field_name': field_name}
                        if not hasattr(cls, test_method_name):
                            setattr(cls, test_method_name, test_method)

        return cls