Missing properties in Custom Platfrom API

Hi, i'm creating a plugin to export all MovieClips from a library to a custom format using "Custom Platfrom SDK" (CPSDK)
And so, when I approached implementation of exporting "9-slice" MovieClips, I began to look for a way to get a rectangle with coordinates for it in "DOM" headers, but I did not find it. I also tried to look for some code in sample plugin, but I also did not find anything that could be related to this.
I noticed that jsfl API has some similarities to headers that are provided in CPSDK and since jsfl documentation is much more convenient (for me) than CPSDK docs I started looking for ways to get what I want there.
I found that "symbolItem" (aka DOM::LibraryItem::ISymbolItem in C++) has a scalingGridRect method to get "a Rectangle object that specifies the locations of the four 9-slice guides", exactly what I need.
Also here I need properties like "sourceFilePath".
But in CPSDK there is only a lone GetTimeLine function.

So ISymbolItem has a lot of missing properties
Is there any way to get at least a 9-slice rect?