+ /**
+ * Gets identifier of augmentation node
+ *
+ * Returned identifier of augmentation node contains all possible
+ * direct child QNames.
+ *
+ * This is sufficient to identify instance of augmentation,
+ * since RFC6020 states that <code>augment</code> that augment
+ * statement must not add multiple nodes from same namespace
+ * / module
+ * to the target node.
+ *
+ * @return Identifier which uniquelly identifies augmentation in particular subtree.
+ *
+ */