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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 mix(self, ca, cb, xb):
 """Mix colors. Args: ca (gdk.RGBA):
 first color cb (gdk.RGBA):
 second color xb (float):
 between 0.0 and 1.0 Return: gdk.RGBA: linear interpolation between ca and cb, 0 or 1 return the unaltered 1st or 2nd color respectively, as in CSS. """

        r = (1 - xb) * ca.red + xb * cb.red
        g = (1 - xb) * ca.green + xb * cb.green
        b = (1 - xb) * ca.blue + xb * cb.blue
        a = (1 - xb) * ca.alpha + xb * cb.alpha
        return gdk.RGBA(red=r, green=g, blue=b, alpha=a)