exact Or.inr e_mem
case refine'_1.inl
α : Type u_1
M : Matroid α
I B : Set α
Ys Xs : Set (Set α)
F : Set α
C : M.ModularCut
hC : C.Nonempty
e : α
he : e ∉ M.E
cl_eq_self : (C.extension e).cl F = F
e_mem : e ∈ F ∧ F \ {e} ∈ C
⊢ M.Flat F ∧ F ∉ C ∨ e ∈ F ∧ F \ {e} ∈ C
no goals