∀ {α : Type u} {x : BEq α} {x_1 : Hashable α} {β : Type v} {m : Std.ExtDHashMap α fun x => β} [inst : EquivBEq α]
  [inst_1 : LawfulHashable α] {l : List (α × β)}, (Std.ExtDHashMap.Const.insertMany m l = ∅) = (m = ∅ ∧ l = [])