∀ {α : Type u} {β : α → Type v} (m : Std.DHashMap.Internal.Raw₀ α β) [inst : BEq α] [inst_1 : Hashable α]
  [inst_2 : LawfulBEq α],
  (↑m).WF →
    ∀ {l : List ((a : α) × β a)} {k : α} {fallback : β k},
      (List.map Sigma.fst l).contains k = false → (↑(m.insertMany l)).getD k fallback = m.getD k fallback