Gemini model 2.0-flash structured output

[ramirolc02]

[x] I have checked the documentation and related resources and couldn't resolve my bug.

Describe the bug
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Hey! Getting many Pydantic validation errors computing faithfulness and answer_correctness. Guess it depends on model used and StructuredOutput capabilities. Its failing very often.

Ragas version: 0.2.15
Python version: 3.11.10

Code to Reproduce
Share code to reproduce the issue

self.google_llm = LangchainLLMWrapper(
            ChatGoogleGenerativeAI(
                model="gemini-2.0-flash-001",
                temperature=0.1,
                top_p=0.9,
                max_tokens=2048,
            )
        )
self.metrics = [
            context_precision,
            context_recall,
            faithfulness,
            answer_relevancy,
        ]
result = evaluate(
                dataset=dataset,
                metrics=self.metrics,
                llm=self.evaluator_llm,
                embeddings=self.google_embeddings,
                # run_config=RUN_CONFIG,
                # callbacks=[delay_handler],  # Add delay callback
            )

Error trace

Got: 1 validation error for ClassificationWithReason
FN
Field required [type=missing, input_value={'TP': [{'statement': 'Es...d partial solutions.'}]}, input_type=dict]
Got: 1 validation error for NLIStatementOutput
statements.30.verdict
Field required [type=missing, input_value={'statement': 'The conver...ext mentions different'}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.11/v/missing
For troubleshooting, visit: https://python.langchain.com/docs/troubleshooting/errors/OUTPUT_PARSING_FAILURE )
Got: 2 validation errors for NLIStatementOutput
statements.31.reason
Field required [type=missing, input_value={'statement': 'Knowledge-... that leverage domain-'}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.11/v/missing
statements.31.verdict
Field required [type=missing, input_value={'statement': 'Knowledge-... that leverage domain-'}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.11/v/missing

Expected behavior
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Additional context
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