getActivePart() python function as complement to setActivePart()

src/Mod/Assembly/App/AppAssemblyPy.cpp

@@ -78,10 +78,22 @@ static PyObject * setActivePart(PyObject *self, PyObject *args)
 
     Py_Return;
 }
+static PyObject * getActivePart(PyObject *, PyObject *)
+{
+    if (PartDesignGui::ActivePartObject == NULL) {
+        return Py::_None();
+    }
+
+    return PartDesignGui::ActivePartObject->getPyObject();
+}
+
 /* registration table  */
 struct PyMethodDef Assembly_methods[] = {
     {"setActivePart"       ,setActivePart      ,METH_VARARGS,
      "setActivePart(BodyObject) -- Set the PartBody object in work."},
 
+    {"getActivePart"       ,getActivePart      ,METH_NOARGS,
+     "getActivePart() -- Get the PartBody object in work."},
+
     {NULL, NULL}        /* end of table marker */
 };