Revert "libs: pregel: find_subgraph_pregel: Do not search via introspection"

This reverts commit 2458f2d2e0.

libs/langgraph/langgraph/pregel/utils.py

@@ -1,6 +1,7 @@
 from typing import Optional
 
 from langchain_core.runnables import RunnableLambda, RunnableSequence
+from langchain_core.runnables.utils import get_function_nonlocals
 
 from langgraph.checkpoint.base import ChannelVersions
 from langgraph.pregel.protocol import PregelProtocol
@@ -41,5 +42,16 @@ def find_subgraph_pregel(candidate: Runnable) -> Optional[PregelProtocol]:
             candidates.extend(c.steps)
         elif isinstance(c, RunnableLambda):
             candidates.extend(c.deps)
+        elif isinstance(c, RunnableCallable):
+            if c.func is not None:
+                candidates.extend(
+                    nl.__self__ if hasattr(nl, "__self__") else nl
+                    for nl in get_function_nonlocals(c.func)
+                )
+            elif c.afunc is not None:
+                candidates.extend(
+                    nl.__self__ if hasattr(nl, "__self__") else nl
+                    for nl in get_function_nonlocals(c.afunc)
+                )
 
     return None