induction as
α : Type u
inst✝ : Category α
as bs : List α
⊢ 𝟙 as ++ 𝟙 bs = 𝟙 (as ++ bs)
case nil
α : Type u
inst✝ : Category α
bs : List α
⊢ 𝟙 [] ++ 𝟙 bs = 𝟙 ([] ++ bs)

case cons
α : Type u
inst✝ : Category α
bs : List α
head✝ : α
tail✝ : List α
tail_ih✝ : 𝟙 tail✝ ++ 𝟙 bs = 𝟙 (tail✝ ++ bs)
⊢ 𝟙 (head✝ :: tail✝) ++ 𝟙 bs = 𝟙 (head✝ :: tail✝ ++ bs)