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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 __lazy_migration(self, master_id):
 """ Creates a revision for a master id that didn't previously have a revision, this allows you to easily turn on revisioning for a collection that didn't previously allow for it. :param master_id: :returns: list of objects """

        collection_name = self.request.headers.get("collection")

        if collection_name:
            stack = AsyncSchedulableDocumentRevisionStack(collection_name,
                                                          self.settings,
                                                          master_id=master_id,
                                                          )
            objects = yield stack._lazy_migration(meta=self._get_meta_data())
            raise Return(objects)

        self.raise_error(500, "This object %s/%s didn't exist as a revision, "
                         "we tried to create it but we failed... Sorry. "
                         "Please check this object" % (collection_name,
                                                       master_id))
        raise Return(None)