def bbox(self):
        """returns a bounding box for the input Path object in the form
        (xmin, xmax, ymin, ymax)."""
        bbs = [seg.bbox() for seg in self._segments]
        xmins, xmaxs, ymins, ymaxs = list(zip(*bbs))
        xmin = min(xmins)
        xmax = max(xmaxs)
        ymin = min(ymins)
        ymax = max(ymaxs)
        return xmin, xmax, ymin, ymax
returns a bounding box for the input Path object in the form
        (xmin, xmax, ymin, ymax).