isdatadescriptor() was added recently.

Doc/lib/libinspect.tex

@@ -184,6 +184,7 @@ Note:
   Typically, data descriptors will also have __name__ and __doc__ attributes 
   (properties, getsets, and members have both of these attributes), but this 
   is not guaranteed.
+\versionadded{2.3}
 \end{funcdesc}
 
 \subsection{Retrieving source code