DocIterator doc_iterator_begin(Buffer const * buf, Inset const * inset = 0);
DocIterator doc_iterator_end(Buffer const * buf, Inset const * inset = 0);
DocIterator doc_iterator_begin(Buffer const * buf, Inset const * inset = 0);
DocIterator doc_iterator_end(Buffer const * buf, Inset const * inset = 0);