no goals
α : Type u
β : Type v
γ : Type w
l : List α
a : α
⊢ sublists (l ++ [a]) = sublists l ++ map (fun x => x ++ [a]) (sublists l)
rw [sublists_append, sublists_singleton, bind_eq_bind, cons_bind, cons_bind, nil_bind,
   map_id' append_nil, append_nil]