How can get list fonts of document in FrameMaker by FDK?

Ex:  Get lists of families of a Session

UIntT i, j; F_StringsT families, weights, variations, angles; F_FontsT perms;

/* Get lists of families, variations, weights, and angles. */

families = F_ApiGetStrings(0, FV_SessionId, FP_FontFamilyNames);

weights = F_ApiGetStrings(0, FV_SessionId, FP_FontWeightNames);

variations = F_ApiGetStrings(0, FV_SessionId, FP_FontVariationNames);

angles = F_ApiGetStrings(0, FV_SessionId, FP_FontAngleNames);

But i change SessionID by DocID, It can't resturn values.

I want get list font using in a document.

How can get list fonts of document in FrameMaker by FDK?