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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 add_entry_point(self, destination):
        '''\
        Add an entry point

        :param destination: node to route to initially
        :type destination: str
        '''
        self.routes.setdefault('__entry_point', set()).add(destination)
        return self.routes['__entry_point']