The GuiDialogShell Object

The GuiDialogShell Object as per the SAP Gui Scripting Spy (Screen reader) is a child of the MainWindow. But the SAP Automation Framework returns null if we use its API s to get the parent of a DialogShell which actually hints it top be a TopLevelWindow. So are dialog shells children of MainWindow or owned by MainWindow or is it a toplevel object itself ? Can anyone please explain this ambiguity..