internal merge of PR #1043
internal merge of PR #1043

PiperOrigin-RevId: 211866054

vthorsteinsson/tensor2tensor,vthorsteinsson/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor