Returns a list of two selection sets similar to those passed to sssetfirst. The first element in the list is a selection set of entities that are gripped but not selected. The second element is a selection set of entities that are both gripped and selected. Either (or both) elements of the list can be nil.
Note Only entities from the current drawing's model space and paper space, not nongraphical objects or entities in other block definitions, can be analyzed by this function.