def clip_units(unit)
      Kernel.raise ArgumentError, "Unknown clip unit #{unit}" unless %w[userspace userspaceonuse objectboundingbox].include?(unit.downcase)
      primitive "clip-units #{unit}"
    end
def clip_units(unit)
      Kernel.raise ArgumentError, "Unknown clip unit #{unit}" unless %w[userspace userspaceonuse objectboundingbox].include?(unit.downcase)
      primitive "clip-units #{unit}"
    end
Define the clip units