∀ {α : Type u} {β : α → Type v} (m : Std.DHashMap.Internal.Raw₀ α β) [inst : BEq α] [inst_1 : Hashable α] [EquivBEq α]
  [LawfulHashable α],
  (↑m).WF →
    ∀ {l : List ((a : α) × β a)} {k k' fallback : α},
      (k == k') = true →
        List.Pairwise (fun a b => (a.fst == b.fst) = false) l →
          k ∈ List.map Sigma.fst l → (↑(m.insertMany l)).getKeyD k' fallback = k