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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 _store_instance_id(self):
        '''
        Run at the initialization before calling any code at agent-side.
        Ensures that descriptor holds our value, this effectively creates a
        lock on the descriptor - if other instance is running somewhere out
        there it would get the notification update and suicide.
        '''

        def do_set(desc):
            desc.instance_id = self._instance_id
            desc.under_restart = None

        return self.update_descriptor(do_set)