def add_filter(self, name, func):
        self.filters[name] = func
From the Py3 str docstring:
dataset/ETHPy150Open adampresley/bottlepy-bootstrap/app/bottle.py/Router.add_filter--crossover with--dataset/ETHPy150Open OpenCobolIDE/OpenCobolIDE/open_cobol_ide/extlibs/future/types/newstr.py/newstr.__new__