∀ {α : Type w} {m : Type w → Type w'} {β : Type w} [inst : Std.Iterator α m β] {it : Std.IterM m β}
  {it' : Std.IterM m β} {out : β} {k : ℕ},
  it.internalState.inner.IsPlausibleStep (Std.IterStep.yield it' out) →
    it.internalState.remaining = k + 1 →
      Std.Iterators.Types.Drop.PlausibleStep it (Std.IterStep.skip (Std.IterM.drop k it'))