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