def hsl_color(hue, saturation, lightness, alpha = nil)
      attrs = {:hue => hue, :saturation => saturation, :lightness => lightness}
      attrs[:alpha] = alpha if alpha
      Color.new(attrs)
    end
def hsl_color(hue, saturation, lightness, alpha = nil)
      attrs = {:hue => hue, :saturation => saturation, :lightness => lightness}
      attrs[:alpha] = alpha if alpha
      Color.new(attrs)
    end
Construct a Sass Color from hsl values.

 @param hue [::Number] The hue of the color in degrees.
   A non-negative number, usually less than 360.
 @param saturation [::Number] The saturation of the color.
   Must be between 0 and 100 inclusive.
 @param lightness [::Number] The lightness of the color.
   Must be between 0 and 100 inclusive.
 @param alpha [::Number] The alpha channel. A number between 0 and 1.

 @return [Sass::Script::Value::Color] the color object