+ /**
+ * Returns a depth-first iterator at the beginning of the child RowItem
+ * tree.
+ */
+ iterator begin();
+
+ /**
+ * Returns a depth-first iterator at the end of the child RowItem tree.
+ */
+ iterator end();
+
+ /**
+ * Returns a constant depth-first iterator at the beginning of the
+ * child RowItem tree.
+ */
+ const_iterator begin() const;
+
+ /**
+ * Returns a constant depth-first iterator at the end of the child
+ * RowItem tree.
+ */
+ const_iterator end() const;
+