∀ {ρ : Type u} {α : Type v} {γ : Type x} {m : Type x → Type x'} [Monad m] {x : Membership α ρ}
  [inst : ForIn' m ρ α inferInstance] {r s : ρ} {init : γ} {f : (a : α) → a ∈ r → γ → m (ForInStep γ)} (h : r = s),
  forIn' r init f = forIn' s init fun a h' acc => f a ⋯ acc