code: def done(self, taskid):
          '''Mark task done'''
          if taskid in self.processing:
              self.mutex.acquire()
              if taskid in self.processing:
                  del self.processing[taskid]
              self.mutex.release()
              return True
          return Falsf done(self, taskid):
          '''Mark task done'''
          if taskid in self.processing:
              self.mutex.acquire()
              if taskid in self.processing:
                  del self.processing[taskid]
              self.mutex.release()
              return True
          return False
docs: Mark task done