∀ {α : Type u} {x : BEq α} {x_1 : Hashable α} {m : Std.ExtHashSet α} [inst : EquivBEq α] [inst_1 : LawfulHashable α]
  {k a : α}, (m.insert k).contains a = true → ¬((k == a) = true ∧ m.contains k = false) → m.contains a = true