Outlining: how to get from ParseData on OutliningNode?

            RootFormula rf = document.SemanticParseData as RootFormula;
            if (rf != null)
            {
                CollapsibleNodeOutliningParser cnop = new CollapsibleNodeOutliningParser();
                foreach (FormulaBody fb in rf.FindAllOfType<FormulaBody>())
                {
                    cnop.Add(new CollapsibleNodeOutliningParserData(fb.StartOffset, OutliningNodeAction.Start, fb));
                    cnop.Add(new CollapsibleNodeOutliningParserData(fb.EndOffset, OutliningNodeAction.End, fb));
                }
                return cnop.UpdateOutlining(document, new TextRange(0, document.Length));
            }
            return TextRange.Deleted;