I have practiced the steps followed by the tutorial to create a sub circuit for half adder, by using existing project stored in fossee file under subcircuit library I have selected Half adder, an already constructed circuit opens up and I have annotated and,in the netlist menu I have put spice to default and generated a netlist and saved that gone back  to eSim window I selected convert kicad to ngspice, but a pop window appears that the sub circuit doesn't contains any kicad netlist, why?, Please give a reply for me.