code: def invert(color):
      
      if isinstance(color, Number):
          # invert(n) and invert(n%) are CSS3 filters and should be left
          # intact
          return String.unquoted("invert(%s)" % (color.render(),))
  
      expect_type(color, Color)
      r, g, b, a = color.rgba
      return Color.from_rgb(1 - r, 1 - g, 1 - b, alpha=a)
docs: Returns the inverse (negative) of a color.  The red, green, and blue
      values are inverted, while the opacity is left alone.