fact: Definition qzt_empty := let mkn t := QztNode t t t t in let n2 := mkn (mkn QztNil) in QztHubNode (mkn n2) n2 n2 n2.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color coloring quiz cfmap) fourcolor(cfquiz cfreducible)