我有一個觸發 Lambda 的 AWS Stepfunction。不幸的是，我無法正確解碼輸入：從 AWS Stepfunction 到 Lambda 的輸入：{  "MessageNumber": 0,  "message": {    "MessageId": "ae5b5d59-6829-4a19-b508-2ba35614e2de",    "ReceiptHandle": "AQEBJsP+Et+WcgstIR9kkA3sH4UDoxYYcoDT2YYa30K87Rx2wSEFaZNg3CNdsjE18LSDMNXWg7VoV/s/p0bSL0PaUxQ0FV34RAwavG0iGMi",    "MD5OfBody": "a726ec7fdda41e454850580e1a2cf4b4",    "Body": "{'stage': 'tst', 'directory': '\\\\\\\\mydomain\\\\data\\\\results', 'variableFilters': ['\\\\filters\\\\x1.txt', '\\\\filters\\\\a1.txt']}",    "Attributes": {      "SenderId": "xxx",      "ApproximateFirstReceiveTimestamp": "xxx",      "ApproximateReceiveCount": "2",      "SentTimestamp": "xxx",      "SequenceNumber": "xxx",      "MessageDeduplicationId": "xxx",      "MessageGroupId": "1"    }  }}Python代碼如下：def lambda_handler(event, context):    print(f'Received Event: {event}')    try:        body = json.loads(event.get('message').get('Body'))        stage = body["stage"]        directory= body["directory"]    except Exception as e:        return (e)我收到錯誤：{  "errorMessage": "Unable to marshal response: JSONDecodeError('Expecting property name enclosed in double quotes: line 1 column 2 (char 1)') is not JSON serializable",  "errorType": "Runtime.MarshalError"}有人知道如何解決這個問題嗎？