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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 fence_draw_callback(self, points):
        '''callback from drawing a fence'''
        self.fenceloader.clear()
        if len(points) < 3:
            return
        self.fenceloader.target_system = self.target_system
        self.fenceloader.target_component = self.target_component
        bounds = mp_util.polygon_bounds(points)
        (lat, lon, width, height) = bounds
        center = (lat+width/2, lon+height/2)
        self.fenceloader.add_latlon(center[0], center[1])
        for p in points:
            self.fenceloader.add_latlon(p[0], p[1])
        # close it
        self.fenceloader.add_latlon(points[0][0], points[0][1])
        self.send_fence()
        self.have_list = True