docs: def get(self, now):
          """
          Get a bucket key to compact.  If none are available, returns
          None.  This uses a configured lock to ensure that the bucket
          key is popped off the sorted set in an atomic fashion.
  
          :param now: The current time, as a float.  Used to ensure the
                      bucket key has been aged sufficiently to be
                      quiescent.
  
          :returns: A bucket key ready for compaction, or None if no
                    bucket keys are available or none have aged
                    sufficiently.
          """
  
          with self.lock:
              items = self.db.zrangebyscore(self.key, 0, now - self.min_age,
                                            start=0, num=1)
              # Did we get any items?
              if not items:
                  return None
  
              # Drop the item we got
              item = items[0]
              self.db.zrem(item)
  
              return item