fact: Definition cardinality (M : Metacategory) : nat := M.cardinal (P.filter (fun '(dom, cod) v => ((dom =? v)%nat && (cod =? v)%nat)%bool) (pairs M)).
imports: Coq.Structures.DecidableTypeEx Coq.FSets.FMapFacts Category.Lib.FMapExt Coq.Arith.PeanoNat Category.Lib Category.Theory.Category