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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 retrieve_asset(self, sid, default_none=False):
 """ Retrieve the Asset for a given sid. """

        try:
            asset = self._asset_cache[sid]
            if asset is None and not default_none:
                raise SidsNotFound(sids=[sid])
            return asset
        except KeyError:
            raise SidsNotFound(sids=[sid])