∀ {F : Type u_1} {α : Type u_2} {β : Type u_3} [inst : DecidableEq α] [inst_1 : DecidableEq β]
  [inst_2 : SemilatticeSup α] [inst_3 : SemilatticeSup β] [inst_4 : FunLike F α β] [SupHomClass F α β] (f : F)
  (hf : Function.Injective ⇑f) (s t : Finset α),
  Finset.map { toFun := ⇑f, inj' := hf } (s ⊻ t) =
    Finset.map { toFun := ⇑f, inj' := hf } s ⊻ Finset.map { toFun := ⇑f, inj' := hf } t