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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 rgba_to_int(cls, red, green, blue, alpha):
 """ Encodes the color as an Integer in RGBA encoding Returns None if any of red, green or blue are None. If alpha is None we use 255 by default. :return: Integer :rtype: int """

        red = unwrap(red)
        green = unwrap(green)
        blue = unwrap(blue)
        alpha = unwrap(alpha)
        if red is None or green is None or blue is None:
            return None
        if alpha is None:
            alpha = 255
        r = red << 24
        g = green << 16
        b = blue << 8
        a = alpha << 0
        rgba_int = r+g+b+a
        if (rgba_int > (2**31-1)):       # convert to signed 32-bit int
            rgba_int = rgba_int - 2**32
        return rgba_int