def addFilter(self, filter):
        if not (filter in self.filters):
            self.filters.append(filter)
Register the class implementing this config, so we only add it once.
dataset/ETHPy150Open babble/babble/include/jython/Lib/logging/__init__.py/Filterer.addFilter--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/endpoints/api_backend_service.py/ApiConfigRegistry.__register_class