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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 unset(self, key):
 """Unset on all references :param key: The key to be unset """

        key = key.strip().upper()
        if key not in dir(default_settings) and key not in self._defaults:
            self.logger.debug("Unset %s", key)
            delattr(self, key)
            self.store.pop(key, None)