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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 register_feature(self, var):
 """ Register a feature with the namespace variable `var`. If the feature is already registered or part of the default :xep:`30` features, a :class:`ValueError` is raised. """

        if var in self._features or var in self.STATIC_FEATURES:
            raise ValueError("feature already claimed: {!r}".format(var))
        self._features.add(var)
        self.on_info_changed()