code: private boolean doVisitChildren(VisitContext context, boolean visitRows) {
  
          // Just need to check whether there are any ids under this
          // subtree.  Make sure row index is cleared out since 
          // getSubtreeIdsToVisit() needs our row-less client id.
          if (visitRows) {
              setRowIndex(-1);
          }
          Collection<String> idsToVisit = context.getSubtreeIdsToVisit(this);
          assert(idsToVisit != null);
  
          // All ids or non-empty collection means we need to visit our children.
          return (!idsToVisit.isEmpty());
      }
docs: a tree visit