def METHOD_NAME(self, cursor, oid, serial, blob_lock=None):
    blob_filename = self._cachedLoadBlobInternal(oid, serial)
    if not blob_filename:
        # All the blobs are in a shared directory. If the file
        # isn't here, it's not anywhere.
        raise POSKeyError(oid, serial=serial, blob_filename=blob_filename)
    return blob_filename