∀ {α : Type u} {β : α → Type v} [inst : BEq α] {l : List ((a : α) × β a)} {k k' : α} {v' : β k'},
  (k' == k) = false → Std.Internal.List.eraseKey k (⟨k', v'⟩ :: l) = ⟨k', v'⟩ :: Std.Internal.List.eraseKey k l