docs: public AbstractProject getBuildingUpstream() {
          Set<Task> unblockedTasks = Jenkins.getInstance().getQueue().getUnblockedTasks();
  
          for (AbstractProject tup : getTransitiveUpstreamProjects()) {
  			if (tup!=this && (tup.isBuilding() || unblockedTasks.contains(tup)))
                  return tup;
          }
          return null;
      }