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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 delete_instance_if_removed(self, port):
 """Enqueue instance delete if it's no longer in the db"""

        instance_type = self.get_instance_type(port)
        if not instance_type:
            return
        if not db_lib.instance_provisioned(port['device_id']):
            i_res = MechResource(port['device_id'], instance_type,
                                 a_const.DELETE)
            self.provision_queue.put(i_res)