actually use input key (#8136)

libs/langchain/langchain/chains/openai_functions/openapi.py

@@ -212,8 +212,8 @@ class SimpleRequestChain(Chain):
     ) -> Dict[str, Any]:
         """Run the logic of this chain and return the output."""
         _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
-        name = inputs["function"].pop("name")
-        args = inputs["function"].pop("arguments")
+        name = inputs[self.input_key].pop("name")
+        args = inputs[self.input_key].pop("arguments")
         _pretty_name = get_colored_text(name, "green")
         _pretty_args = get_colored_text(json.dumps(args, indent=2), "green")
         _text = f"Calling endpoint {_pretty_name} with arguments:\n" + _pretty_args