∀ {σ : Type u_1} {f : σ → Option σ} {a : σ} {b : Option σ} [inst : SizeOf σ] (steps : ℕ)
  (evals_in_steps : (flip bind f)^[steps] (some a) = b),
  sizeOf { steps := steps, evals_in_steps := evals_in_steps } = 1 + sizeOf steps + sizeOf evals_in_steps