def _write_version(self, data, model):
vdata = {'<STR_LIT:data>': data,<EOL>'<STR_LIT:key>': model.key,<EOL>'<STR_LIT>': model.Meta.bucket_name,<EOL>'<STR_LIT>': time.time()}<EOL>obj = version_bucket.new(data=vdata)<EOL>obj.add_index('<STR_LIT>', model.key)<EOL>obj.add_index('<STR_LIT>', vdata['<STR_LIT>'])<EOL>obj.add_index('<STR_LIT>', int(vdata['<STR_LIT>']))<EOL>obj.store()<EOL>return obj.key<EOL>
Writes a copy of the objects current state to write-once mirror bucket.

Args:
    data (dict): Model instance's all data for versioning.
    model (instance): Model instance.

Returns:
    Key of version record.
    key (str): Version_bucket key.