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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 display_fence(self):
        '''display the fence'''
        from MAVProxy.modules.mavproxy_map import mp_slipmap
        self.fence_change_time = self.module('fence').fenceloader.last_change
        points = self.module('fence').fenceloader.polygon()
        self.mpstate.map.add_object(mp_slipmap.SlipClearLayer('Fence'))
        if len(points) > 1:
            popup = MPMenuSubMenu('Popup',
                                  items=[MPMenuItem('FencePoint Remove', returnkey='popupFenceRemove'),
                                         MPMenuItem('FencePoint Move', returnkey='popupFenceMove')])
            self.mpstate.map.add_object(mp_slipmap.SlipPolygon('Fence', points, layer=1,
                                                               linewidth=2, colour=(0,255,0), popup_menu=popup))