From 1cf117ed9d4d0d2899abe591dbaf64cf159ee635 Mon Sep 17 00:00:00 2001
From: Nuno Campos <nuno@langchain.dev>
Date: Thu, 19 Sep 2024 17:09:04 -0700
Subject: [PATCH] Lint

---
 libs/langgraph/langgraph/utils/runnable.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libs/langgraph/langgraph/utils/runnable.py b/libs/langgraph/langgraph/utils/runnable.py
index 7471f0008..bfc2a627b 100644
--- a/libs/langgraph/langgraph/utils/runnable.py
+++ b/libs/langgraph/langgraph/utils/runnable.py
@@ -107,7 +107,9 @@ class RunnableCallable(Runnable):
         self.trace = trace
         self.recurse = recurse
         # check signature
-        params = inspect.signature(func or afunc).parameters
+        if func is None and afunc is None:
+            raise ValueError("At least one of func or afunc must be provided.")
+        params = inspect.signature(cast(Callable, func or afunc)).parameters
         self.func_accepts_config = "config" in params
         self.func_accepts: dict[str, bool] = {}
         for kw, typ, _, _ in KWARGS_CONFIG_KEYS: