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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 reset(self, subject_id, entity_id):
 """ Scrap the assertions received from a IdP or an AA about a special subject. :param subject_id: The subjects identifier :param entity_id: The identifier of the entity_id of the assertion :return: """

        if not self._cache.set(_key(subject_id, entity_id), {}, 0):
            raise CacheError("reset failed")