∀ {σ : Type u_1} {f : σ → Option σ} {a : σ} {b : Option σ} {m : ℕ} [inst : SizeOf σ]
  (toEvalsTo : StateTransition.EvalsTo f a b) (steps_le_m : toEvalsTo.steps ≤ m),
  sizeOf { toEvalsTo := toEvalsTo, steps_le_m := steps_le_m } = 1 + sizeOf toEvalsTo + sizeOf steps_le_m