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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 get_boundingbox(self):
 """ Return minimum and maximum x and z coordinates of the chunks that make up this world save """

        b = BoundingBox()
        for rx,rz in self.regionfiles.keys():
            region = self.get_region(rx,rz)
            rx,rz = 32*rx,32*rz
            for cc in region.get_chunk_coords():
                x,z = (rx+cc['x'],rz+cc['z'])
                b.expand(x,None,z)
        return b