def plural(self, rule, replacement):
    self.plurals[0:0] = [tuple([rule, replacement])]
When no child element is a form, None is returned.
dataset/ETHPy150Open rsms/smisk/lib/smisk/inflection/__init__.py/Inflector.plural--crossover with--dataset/ETHPy150Open ralphm/wokkel/wokkel/test/test_data_form.py/FindFormTest.test_noForm