解决TF升级到1.5之后seq2seq.py出现的引用报错：
1.4时候使用rnn_cell_impl的_Linear没有问题的，TF升级到1.5之后这一行就运行不过去了，查到的方法是引用core_rnn_cell下的_Linear.
1 from tensorflow.contrib.rnn.python.ops import core_rnn_cell 2 from tensorflow.python.framework import dtypes 3 from tensorflow.python.framework import ops 4 from tensorflow.python.ops import array_ops 5 from tensorflow.python.ops import control_flow_ops 6 from tensorflow.python.ops import embedding_ops 7 from tensorflow.python.ops import math_ops 8 from tensorflow.python.ops import nn_ops 9 from tensorflow.python.ops import rnn 10 from tensorflow.python.ops import rnn_cell_impl 11 from tensorflow.python.ops import variable_scope 12 from tensorflow.python.util import nest 13 14 # TODO(ebrevdo): Remove once _linear is fully deprecated. 15 Linear = core_rnn_cell._Linear # pylint: disable=protected-access,invalid-name