langchain/tools/sql_database/tool.py/QueryCheckerTool/initialize_llm_chain
class QueryCheckerTool:    def initialize_llm_chain(cls, values: Dict[str, Any]) -> Dict[str, Any]:
        if "llm_chain" not in values:
            values["llm_chain"] = LLMChain(
                llm=values.get("llm"),
                prompt=PromptTemplate(
                    template=QUERY_CHECKER, input_variables=["query", "dialect"]
                ),
            )

        if values["llm_chain"].prompt.input_variables != ["query", "dialect"]:
            raise ValueError(
                "LLM chain for QueryCheckerTool must have input variables ['query', 'dialect']"
            )

        return values