proposition: Lemma sparse_cons x p : sparse (x :: p) = ~~ has (cnode x) p && sparse p.
proof: Proof. exact: (@simple_cons (permF G)). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap walkup geometry color chromogram)