呼叫PutMetricalArm操作时发生错误（验证Error）：无效的指标列表

Question

我将在下面的问题上使用put_metric_alarm函数在python中创建警报时，

[ERROR] ClientError: An error occurred (ValidationError) when calling the PutMetricAlarm 
operation: Invalid metrics list
Traceback (most recent call last):
File "/var/task/manage_alarms.py", line 672, in handle_alarms
manage_alarms(cluster_name, sns, sections, namespace, None, None, None,None)
File "/var/task/manage_alarms.py", line 584, in manage_alarms
create_alarm(alarm_name, metric_json, alarm_json,sns)
File "/var/task/manage_alarms.py", line 262, in create_alarm
response = client.put_metric_alarm(AlarmName=alarm_name,
AlarmDescription=alarm_json['Description'],
File "/var/runtime/botocore/client.py", line 391, in _api_call
return self._make_api_call(operation_name, kwargs)
File "/var/runtime/botocore/client.py", line 719, in _make_api_call
raise error_class(parsed_response, operation_name)

我会发送有效载荷，如下

metric_stat_json = [{'Id': 'bytesdropcountblackhole_math', 'MetricStat': {'Metric': 
{'MetricName': 'bytesdropcountblackhole', 'Namespace': 'AWS/TransitGateway', 'Dimensions': 
[{'Name': 'TransitGateway', 'Value': 'tgw-09a7a181c16936efb'}]}, 'Period': 300, 'Stat': 
'Average', 'Unit': 'Count'}, 'ReturnData': False}, {'Id': 'bytesdropcountblackhole_expr', 
'Expression': 'DIFF(bytesdropcountblackhole_math)', 'ReturnData': True}]

response=client.put_metric_alarm(AlarmName=alarm_name, AlarmDescription=alarm_json['Description'],
                        ComparisonOperator=alarm_json['Comparison'], EvaluationPeriods=alarm_json['EvalPeriod'],AlarmActions=[sns],
                        InsufficientDataActions=[sns],OKActions=[sns],Threshold=set_val,Metrics=metric_stat_json,Tags=tags)