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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 drawing_update(self):
        '''update line drawing'''
        from MAVProxy.modules.mavproxy_map import mp_slipmap
        if self.draw_callback is None:
            return
        self.draw_line.append(self.click_position)
        if len(self.draw_line) > 1:
            self.mpstate.map.add_object(mp_slipmap.SlipPolygon('drawing', self.draw_line,
                                                          layer='Drawing', linewidth=2, colour=(128,128,255)))