text: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  # Copyright 1999-2017 Alibaba Group Holding Ltd.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  from .core import Operand
  from .. import opcodes as OperandDef
  from ..serialize import StringField, ListField, ValueType
  from ..utils import to_str
  
  
  class Fetch(Operand):
      _op_type_ = OperandDef.FETCH
  
      _to_fetch_key = StringField('to_fetch_key', on_serialize=to_str)
  
      @property
      def to_fetch_key(self):
          return self._to_fetch_key
  
  
  class FetchShuffle(Operand):
      _op_type_ = OperandDef.FETCH_SHUFFLE
  
      _to_fetch_keys = ListField('to_fetch_keys', ValueType.string,
                                 on_serialize=lambda v: [to_str(i) for i in v])
  
      @property
      def to_fetch_keys(self):
          return self._to_fetch_keys
  