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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 authenticated(f):
 """Decorator that authenticates to Keystone automatically."""

    @wraps(f)
    def new_f(self, *args, **kwargs):
        if not self.nova_client.client.auth_token:
            self.authenticate()
        return f(self, *args, **kwargs)
    return new_f