docs: private void findTargets(final IndexTerm term) {
          final List<IndexTerm> subTerms = term.getSubTerms();
          List<IndexTermTarget> subTargets = null;
          if (subTerms != null && ! subTerms.isEmpty()){
              for (final IndexTerm subTerm : subTerms) {
                  subTargets = subTerm.getTargetList();
                  if (subTargets != null && !subTargets.isEmpty()) {
                      //findTargets(subTerm);
                      //add targets(child term)
                      term.addTargets(subTerm.getTargetList());
                  } else {
                      //term.addTargets(subTerm.getTargetList());
                      //recursive search child's child term
                      findTargets(subTerm);
                  }
                  //add target to parent indexterm
                  term.addTargets(subTerm.getTargetList());
              }
  
          }
      }