proposition: Lemma deg_Knm_l n m (x : 'I_n) : #|N(inl x : 'K_n,m)| = m.
proof: Proof. by rewrite opn_Knm_l card_imset ?cardsT ?card_ord //; exact: inr_inj. Qed.
imports: Coq(Setoid CMorphisms) mathcomp(all_ssreflect) GraphTheory(edone preliminaries bij digraph) GraphTheory(set_tac)