refine ⟨fun h ↦ h.subset_ground_of_mem, fun h ↦ ?_⟩
case inr.intro
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i✝ j : ι
e f : α
inst✝ : Subsingleton ι
i : ι
⊢ M.ModularFamily Xs ↔ ∀ (i : ι), Xs i ⊆ M.E
case inr.intro
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i✝ j : ι
e f : α
inst✝ : Subsingleton ι
i : ι
h : ∀ (i : ι), Xs i ⊆ M.E
⊢ M.ModularFamily Xs