langchain/chains/api/base.py/APIChain/_call
class APIChain:    def _call(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
        question = inputs[self.question_key]
        api_url = self.api_request_chain.predict(
            question=question,
            api_docs=self.api_docs,
            callbacks=_run_manager.get_child(),
        )
        _run_manager.on_text(api_url, color="green", end="\n", verbose=self.verbose)
        api_response = self.requests_wrapper.get(api_url)
        _run_manager.on_text(
            api_response, color="yellow", end="\n", verbose=self.verbose
        )
        answer = self.api_answer_chain.predict(
            question=question,
            api_docs=self.api_docs,
            api_url=api_url,
            api_response=api_response,
            callbacks=_run_manager.get_child(),
        )
        return {self.output_key: answer}