∀ {G : Type u_1} {β : Type u_3} [inst : Group G] [inst_1 : MulAction G β] {α : Type u_4} [inst_2 : Group α]
  [inst_3 : MulAction α β] [SMulCommClass G α β] (a : α) (b : β),
  MulAction.stabilizer G (a • b) = MulAction.stabilizer G b