函数调用结构化输出json模式不正确

问题描述：

老师我在结构化输出是将with_structured_output切换成json，模型改成gpt-4o，模版提示也加了，但运行时报不能正常提取问题和答案，这是什么情况呀？

langchain_core.exceptions.OutputParserException: Failed to parse QAExtra from completion {"question": null, "answer": null}. Got: 2 validation errors for QAExtra

question

  none is not an allowed value (type=type_error.none.not_allowed)

answer

  none is not an allowed value (type=type_error.none.not_allowed)

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