public static Density KilogramsPerCubicDecimeter <T>(this T value) =>
 Density.FromKilogramsPerCubicDecimeter(Convert.ToDouble(value));
 public void NumberToKilogramsPerCubicDecimeterTest() =>
 Assert.Equal(Density.FromKilogramsPerCubicDecimeter(2), 2.KilogramsPerCubicDecimeter());