PowerPoint.Shape "Convert to Shape" in code

Question

in my Power Point add-in I am loading .svg file within slide using this code

            Slide activeSlide = Globals.ThisAddIn.Application.ActiveWindow.View.Slide;
            PowerPoint.Shape ppPicture = activeSlide.Shapes.AddPicture(testImageUrl, MsoTriState.msoTrue, MsoTriState.msoTrue, 0, 0);
            ppPicture.LinkFormat.SourceFullName = testImageUrl;

then I need to ungroup this file, like it happens when clicking mouse right button and selecting menu point "Convert to Shape".

ppPicture.Ungroup();

throws System.UnauthorizedAccessException: 'This member can only be accessed for a group.'

So how can I do it ?