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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(self, relation):
 """Add the relation inner to the cache, under the schema schema and identifier identifier :param BaseRelation relation: The underlying relation. """

        cached = _CachedRelation(relation)
        logger.debug('Adding relation: {!s}'.format(cached))
        logger.debug('before adding: {}'.format(
            pprint.pformat(self.dump_graph()))
        )
        with self.lock:
            self._setdefault(cached)
        logger.debug('after adding: {}'.format(
            pprint.pformat(self.dump_graph()))
        )