∀ {α β γ δ : Type w} {m : Type w → Type w'} {n : Type w → Type w''} [inst : Monad m] [LawfulMonad m] [inst_2 : Monad n]
  [inst_3 : MonadAttach n] [LawfulMonad n] [WeaklyLawfulMonadAttach n] [inst_6 : MonadLiftT m n] [LawfulMonadLiftT m n]
  [inst_8 : Std.Iterator α m β] [Std.Iterators.Finite α m] {f : β → γ} {g : γ → n (Option δ)} {it : Std.IterM m β},
  (Std.IterM.filterMapM g (Std.IterM.map f it)).toArray = (Std.IterM.filterMapM (fun b => g (f b)) it).toArray