def unlock(self):
        if self._locked:
            _unlock_file(self._file)
            self._locked = False
Used by actor (owner) to rewind port peeking to front token.
dataset/ETHPy150Open babble/babble/include/jython/Lib/mailbox.py/_singlefileMailbox.unlock--crossover with--dataset/ETHPy150Open EricssonResearch/calvin-base/calvin/actor/actorport.py/InPort.peek_rewind