code: public boolean needsSystemTree() {
          if (operands == null) {
              return false;
          }
          for (Iterator<QueryNode> iter = operands.iterator(); iter.hasNext();) {
              QueryNode queryNode = (QueryNode) iter.next();
              if (queryNode.needsSystemTree()) {
                  return true;
              }
          }
          return false;
      }
docs: {@inheritDoc}