code: def delete(self, token):
          
          self._lock.acquire_write()
          try:
              lock = self._dict.get(token)
              _logger.debug("delete {}".format(lock_string(lock)))
              if lock is None:
                  return False
              # Remove url to lock mapping
              key = "URL2TOKEN:{}".format(lock.get("root"))
              if key in self._dict:
                  # _logger.debug("    delete token {} from url {}".format(token, lock.get("root")))
                  tokList = self._dict[key]
                  if len(tokList) > 1:
                      # Note: shelve dictionary returns copies, so we must
                      # reassign values:
                      tokList.remove(token)
                      self._dict[key] = tokList
                  else:
                      del self._dict[key]
              # Remove the lock
              del self._dict[token]
  
              self._flush()
          finally:
              self._lock.release()
          return True
docs: Delete lock.
  
          Returns True on success. False, if token does not exist, or is expired.