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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def draw_cloud(width=140, height=60, color=rgb(255, 255, 255)):
 """ Draw a cloud with the given width, height, and color. """


    cairo_color = color / rgb(255, 255, 255)

    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
    ctx = cairo.Context(surface)

    # A cloud consists of 4 circles
    draw_circle(ctx, width / 3, height / 2, height / 3, cairo_color)
    draw_circle(ctx, 2 * width / 3, height / 2, height / 3, cairo_color)
    draw_circle(ctx, width / 2, height / 3, height / 3, cairo_color)
    draw_circle(ctx, width / 2, 2 * height / 3, height / 3, cairo_color)

    surface.write_to_png('cloud.png')