code: func (itr *resultsItr) GetBookmarkAndClose() string {
  	returnBookmark := ""
  	if queryResultIterator, ok := itr.dbItr.(statedb.QueryResultsIterator); ok {
  		returnBookmark = queryResultIterator.GetBookmarkAndClose()
  	}
  	return returnBookmark
  }
docs: // GetBookmarkAndClose implements method in interface ledger.ResultsIterator