python GIF保存语法

Question

from PIL import Image
import images2gif as i2g
import sys, os

def water(img, watermark):
    mark = Image.open(watermark)
    try:
        im = Image.open(img)
        if im.mode != 'RGBA':
            im = im.convert('RGBA')
        layer = Image.new('RGBA', im.size, (0,0,0,0))
        position = (im.size[0]-mark.size[0], im.size[1]-mark.size[1])
        layer.paste(mark, position)
        frames = i2g.readGif(im, False)
        frames_out = []
        for frame in frames:
            frames_out.append(Image.composite(layer, frame, layer)
            i2g.writeGif('out.gif',frames_out, duration=0.5, dither=0)
    except Exception, (msg):
        print msg

 def test():
    water(sys.argv[1], "water.png")       

if __name__ == '__main__':
    test()            

我想在上面的gif图像上做一个水印。你知道吗

下面是完整的代码，但给出了一个错误：

i2g.writeGif('out.gif',frames_out, duration=0.5, dither=0)
       ^
SyntaxError: invalid syntax

我做错了什么？你知道吗