How to get the segment pair from a segment in EditorController.ContentChanged

Hi, 

I registered the ContentChanged event of the EditorController. 

The event handler passes a list of segments (ISegment). 

How can I get the ISegmentPair that contains the ISegment? 

segment.Parent, segment.ParentParagraph and segment.ParentParagraphUnit are always NULL. 

I'm using Trados Studio 2015 SDK. 

Thanks, 

Christopher