fact: Definition empty : showM := fun _ _ m => monoid_unit m.
imports: Coq.Strings.String Coq.Program.Wf Coq.PArith.BinPos Coq.ZArith.ZArith ExtLib.Structures.Monoid ExtLib.Structures.Reducible ExtLib.Programming.Injection ExtLib.Data.Char ExtLib.Data.String ExtLib.Data.Fun ExtLib.Core.RelDec