docs: public VoidAggregation unpin(long originatorId, long taskId) {
          RequestDescriptor descriptor = RequestDescriptor.createDescriptor(originatorId, taskId);
          VoidAggregation aggregation;
          if ((aggregation = clipboard.get(descriptor)) != null) {
              clipboard.remove(descriptor);
              trackingCounter.decrementAndGet();
  
              // FIXME: we don't want this here
              //            completedQueue.clear();
  
              return aggregation;
          } else
              return null;
      }