have hi := h.iUnion_indep_subset_indep (fun i ↦ (hIs i).subset) (fun i ↦ (hIs i).indep)
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
h : M.SkewFamily Xs
hIs : ∀ (i : ι), M.Basis (Is i) (Xs i)
⊢ M.Basis (⋃ i, Is i) (⋃ i, Xs i)
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
h : M.SkewFamily Xs
hIs : ∀ (i : ι), M.Basis (Is i) (Xs i)
hi : M.Indep (⋃ i, Is i)
⊢ M.Basis (⋃ i, Is i) (⋃ i, Xs i)