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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 update(self, res, pk, depth=1, since=None):
 """ Try to sync an object to the local database, in case of failure where a referenced object is not found, attempt to fetch said object from the REST api """

        fetch = lambda: self._fetcher.fetch_latest(res, pk, 1, since=since)
        self._update(res, fetch, depth)