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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 flatten(image, bgcolor=None):
 """ Flatten an image, with an optional background color """

        if bgcolor:
            background = PIL.Image.new('RGB', image.size, bgcolor)
            background.paste(image, mask=image.split()[3])
            return background

        return image.convert('RGB')