code: def vertical_strip(width=10, height=100, color=rgb(100, 100, 100),
                     subtlety=0.1):
      
  
      cairo_color = color / rgb(255, 255, 255)
  
      surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
      ctx = cairo.Context(surface)
  
      ctx.scale(width / 1.0, height / 1.0)
  
      pat = cairo.LinearGradient(0.0, 0.0, 0.0, 1.0)
      pat.add_color_stop_rgba(
          0,
          cairo_color.red,
          cairo_color.green,
          cairo_color.blue,
          0
      )
      pat.add_color_stop_rgba(
          1,
          cairo_color.red,
          cairo_color.green,
          cairo_color.blue,
          1
      )
  
      ctx.rectangle(0, 0, 1, 1)
      ctx.set_source(pat)
      ctx.fill()
  
      surface.write_to_png('vertical_strip.png')
docs: Draws a subtle vertical gradient strip.