code: public final List<AbstractProject> getBuildTriggerUpstreamProjects() {
          ArrayList<AbstractProject> result = new ArrayList<AbstractProject>();
          for (AbstractProject<?,?> ap : getUpstreamProjects()) {
              BuildTrigger buildTrigger = ap.getPublishersList().get(BuildTrigger.class);
              if (buildTrigger != null)
                  if (buildTrigger.getChildJobs(ap).contains(this))
                      result.add(ap);
          }
          return result;
      }
docs: Returns only those upstream projects that defines {@link BuildTrigger} to this project.
  This is a subset of {@link #getUpstreamProjects()}
  <p>No longer used in the UI.
  @return A List of upstream projects that has a {@link BuildTrigger} to this project.