docs: def deregister(self, event_type, callback, details_filter=None):
          """Remove a single listener bound to event ``event_type``.
  
          :param event_type: deregister listener bound to event_type
          :param callback: callback that was used during registration
          :param details_filter: details filter that was used during
                                 registration
  
          :returns: if a listener was deregistered
          :rtype: boolean
          """
          with self._lock:
              listeners = self._topics.get(event_type, [])
              for i, listener in enumerate(listeners):
                  if listener.is_equivalent(callback,
                                            details_filter=details_filter):
                      listeners.pop(i)
                      return True
              return False