def retrieve(self, path):
        subResult = self.retriever.retrieve(path)
        if subResult is None:
            return None
        return self.resultRetrieved(path, subResult)
Decorating a callable with L{deprecated} emits a warning.
dataset/ETHPy150Open twisted/imaginary/imaginary/idea.py/DelegatingRetriever.retrieve--crossover with--dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/twisted/python/test/test_deprecate.py/TestDeprecationWarnings.test_deprecateEmitsWarning