近期在看模型的时候，因为README.md文件里涉及到了代码，但是markdown文件里代码的变量为Python的关键字str，如下所示，

import time
from bert_base.client import BertClient

with BertClient(show_server_config=False, check_version=False, check_length=False, mode='NER') as bc:
   start_t = time.perf_counter()
   str = '1月24日，新华社对外发布了中央对雄安新区的指导意见，洋洋洒洒1.2万多字，17次提到北京，4次提到天津，信息量很大，其实也回答了人们关心的很多问题。'
   rst = bc.encode([str, str])
   pri

When the code is doing the evaluation, there is an error when returning the evaluation result : result = estimator.evaluate(input_fn=eval_input_fn). Detailed error is probably related to the confusion matrix.
It says that: TypeError: eval_metric_ops[confusion_matrix] must be Operation or Tensor, given: <tf.Variable 'total_confusion_matrix:0' shape=(12, 12) dtype=float64_ref>
my tensorflo