code: func (v *Pattern) AddColorStopRGB(offset, red, green, blue float64) error {
  	C.cairo_pattern_add_color_stop_rgb(v.native(), C.double(offset),
  		C.double(red), C.double(green), C.double(blue))
  	return v.Status().ToError()
  }
docs: // AddColorStopRGB is a wrapper around cairo_pattern_add_color_stop_rgb().