@abstractmethod
    def apply(self, f):
The form type is rendered as a hidden field with name FORM_TYPE.
dataset/ETHPy150Open uwescience/raco/raco/expression/expression.py/Expression.apply--crossover with--dataset/ETHPy150Open ralphm/wokkel/wokkel/test/test_data_form.py/FormTest.test_toElementFormType