* Since the syntax for adding a new element to a map<> or a list<>
* differ, \ref DocEntrySet is designed as an adapter to unify the
* interfaces of \ref DocEntrySet and \ref ElementSet.
* Since the syntax for adding a new element to a map<> or a list<>
* differ, \ref DocEntrySet is designed as an adapter to unify the
* interfaces of \ref DocEntrySet and \ref ElementSet.