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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 spawn_missing_master(self):
        '''
        Notifies the standalone slave agency that the master agency is missing
        '''
        d = defer.succeed(None)
        if callable(self.on_master_missing_cb):
            d.addCallback(defer.drop_param, self.on_master_missing_cb)
        return d