type angle = [ `Deg | `Grad | `Rad ] quantitytype length = [ `Em | `Ex | `Px | `In | `Cm | `Mm | `Pt | `Pc | `Percent ] quantitytype time = [ `S | `Ms ] quantitytype frequency = [ `Hz | `KHz ] quantitySvg_types.UnitSVG defines several units to measure time, length, angles.