   end
 
   defp new_from_list([item | rest], acc) do
-    new_from_list(rest, [{item, []} | acc])
+    new_from_list(rest, [{item, @dummy_value} | acc])
   end
 
   defp new_from_list_transform([], _fun, acc) do
     :maps.from_list(acc)
   end
   defp new_from_list_transform([item | rest], fun, acc) do
-    new_from_list_transform(rest, fun, [{fun.(item), []} | acc])
+    new_from_list_transform(rest, fun, [{fun.(item), @dummy_value} | acc])
   end
 
   @doc """

      %{^key => _} ->
        filter_not_in(rest, map2, acc)
      _ ->
        filter_not_in(rest, map2, [{key, []} | acc])
    end
  end


  `MapSet`s can also be constructed starting from other collection-type data
  structures: for example, see `MapSet.new/1` or `Enum.into/2`.
  """

  # MapSets have an underlying Map. MapSet elements are keys of said map,
  # and this empty list is their associated dummy value.
  @dummy_value []

  @type value :: term

