fact: Definition concatMap {A B} (f : A → list B) : list A → list B := flatten ∘ map f.
imports: Coq.Lists.List Equations(Equations) Equations.Type.EqDec Category.Lib Category.Theory.Coq.Functor Category.Theory.Coq.Applicative Category.Theory.Coq.Monad Category.Theory.Coq.Maybe Coq.Lists.List