def _key_from_fd(self, fd):
        try:
            return self._fd_to_key[fd]
        except KeyError:
            return None
Create a handler instance with payload for a particular slice.
dataset/ETHPy150Open dpkp/kafka-python/kafka/selectors34.py/_BaseSelectorImpl._key_from_fd--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/appengine-mapreduce/python/test/mapreduce/handlers_test.py/MapperWorkerCallbackHandlerLeaseTest._create_handler