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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 buffer(self, distance):
 """ Return a new Extrusion object which is expanded in profile and in height by a specified distance. Returns buffered: Extrusion object """

        distance = float(distance)

        # start with current height
        height = self.primitive.height
        # if current height is negative offset by negative amount
        height += np.sign(height) * 2.0 * distance

        buffered = Extrusion(
            transform=self.primitive.transform.copy(),
            polygon=self.primitive.polygon.buffer(distance),
            height=height)

        # slide the stock along the axis
        buffered.slide(-np.sign(height) * distance)

        return buffered