From dfeff082bbddc63b383de6d55dea18fc208c0bd5 Mon Sep 17 00:00:00 2001
From: William Fu-Hinthorn <13333726+hinthornw@users.noreply.github.com>
Date: Wed, 29 May 2024 06:21:31 -0700
Subject: [PATCH] nit: Better TypeError

---
 langgraph/utils.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/langgraph/utils.py b/langgraph/utils.py
index f04388677..e766a7fb8 100644
--- a/langgraph/utils.py
+++ b/langgraph/utils.py
@@ -73,6 +73,12 @@ class RunnableCallable(Runnable):
         return f"{self.get_name()}({', '.join(f'{k}={v!r}' for k, v in repr_args.items())})"
 
     def invoke(self, input: Any, config: Optional[RunnableConfig] = None) -> Any:
+        if self.func is None:
+            raise TypeError(
+                f'No synchronous function provided to "{self.name}".'
+                "\nEither initialize with a synchronous function or invoke"
+                " via the async API (ainvoke, astream, etc.)"
+            )
         if self.trace:
             ret = self._call_with_config(
                 self.func, input, merge_configs(self.config, config), **self.kwargs