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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 convertShape(shapeString):
 """ Convert xml shape string into float tuples. This method converts the 2d or 3d shape string from SUMO's xml file into a list containing 3d float-tuples. Non existant z coordinates default to zero. If shapeString is empty, an empty list will be returned. """


    cshape = []
    for pointString in shapeString.split():
        p = [float(e) for e in pointString.split(",")]
        if len(p) == 2:
            cshape.append((p[0], p[1], 0.))
        elif len(p) == 3:
            cshape.append(tuple(p))
        else:
            raise ValueError(
                'Invalid shape point "%s", should be either 2d or 3d' % pointString)
    return cshape