return null;
        }
      };
    }

    final Iterator<N> breadthFirst(Iterator<? extends N> startNodes) {
      return topDown(startNodes, InsertionOrder.BACK);
    }

    final Iterator<N> preOrder(Iterator<? extends N> startNodes) {
      return topDown(startNodes, InsertionOrder.FRONT);
    }

    /**
     * In top-down traversal, an ancestor node is always traversed before any of its descendant

                entity.setPassword(encodedPassword);
            }
            return entity;
        });
    }

    /**
     * Creates a label/value map item for dropdowns or list displays.
     *
     * @param label the display label for the item
     * @param value the value associated with the item
     * @return a map containing the label and value entries
     */