∀ {α : Type u} {β : α → Type v} [inst : BEq α] [inst_1 : Hashable α] {m₁ m₂ : Std.DHashMap.Raw α β}
  [inst_2 : LawfulBEq α], m₁.WF → m₂.WF → ∀ {k : α}, (m₁ ∩ m₂).get? k = if k ∈ m₂ then m₁.get? k else none