Theorem: Matroid.contract_empty (Matroid/Minor/Basic.lean)

State before:
α : Type u_1
M✝ M' N : Matroid α
e f : α
I J R B X Y Z K C C₁ C₂ : Set α
M : Matroid α
⊢ M ／ ∅ = M
Tactic:
rw [← dual_delete_dual_eq_contract, delete_empty, dual_dual]
State after:
no goals