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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 create_vehicle_icon(self, name, colour, follow=False, vehicle_type=None):
        '''add a vehicle to the map'''
        from MAVProxy.modules.mavproxy_map import mp_slipmap
        if vehicle_type is None:
            vehicle_type = self.vehicle_type_name
        if name in self.have_vehicle and self.have_vehicle[name] == vehicle_type:
            return
        self.have_vehicle[name] = vehicle_type
        icon = self.mpstate.map.icon(colour + vehicle_type + '.png')
        self.mpstate.map.add_object(mp_slipmap.SlipIcon(name, (0,0), icon, layer=3, rotation=0, follow=follow,
                                                   trail=mp_slipmap.SlipTrail()))