langgraph/how-tos/subgraph-transform-state/

[giscus[bot]]

langgraph/how-tos/subgraph-transform-state/

Build language agents as graphs

https://langchain-ai.github.io/langgraph/how-tos/subgraph-transform-state/

[ezshen]

Hi, I can't seem to get the graph drawing functionality to correctly display the subgraph nodes for this example specifically.

If I run the code above and add the line print(parent_graph.get_graph(xray=2).draw_ascii()), I get the below output, which does not correctly display the nodes child_1 or grandchild_1:

+-----------+  
| __start__ |  
+-----------+  
      *        
      *        
      *        
+----------+   
| parent_1 |   
+----------+   
      *        
      *        
      *        
  +-------+    
  | child |    
  +-------+    
      *        
      *        
      *        
+----------+   
| parent_2 |   
+----------+   
      *        
      *        
      *        
 +---------+   
 | __end__ |   
 +---------+ 

Any ideas? Thanks.

[vbarda]

@ezshen subgraphs are not supported in draw_ascii, you can use

from IPython.display import Image, display
display(Image(parent_graph.get_graph(xray=2).draw_mermaid_png()))

[ezshen]

@vbarda Thanks for getting back to me! I tried again and it still is not displaying the correct nodes for the subgraph. I may be totally off, but It doesn't look like the CompiledGraph is able to find any subgraphs...

print("SUBGRAPHS", dict(parent_graph.get_subgraphs()))
print("MAIN GRAPH", parent_graph.get_graph())
display(Image(parent_graph.get_graph(xray=2).draw_mermaid_png()))

Here is the output I get:

[vbarda]

ah, this is because in this example subgraphs are called inside the functions, so you won't be able to actually render them from the parent graph at the moment. we're not inspecting the function signatures to see if graphs are called when calling app.get_graph()

if you didn't have different schemas, you could pass the compiled graph to add_node

parent_graph.add_node("child", child_graph)

instead of

parent.add_node("child", call_child_graph)

and this would render correctly. hope this helps!

[ezshen]

Got it. Unfortunately, my parent and child graphs have different schemas, but I'll find a workaround! Thanks!

[marcammann]

Similar to the issue with the diagram, something seems to break when using a function to invoke another graph. Can't access the state of subgraphs for some reason. Is there a way to call the subgraph from a function in a way that preserves that?

[marcammann]

Actually, nevermind. The only way to get subgraphs to work is when the Runnable is a compiled Graph itself. So any input/output transformations have to be a RunnableLambda or something similar, leaving the graph as-is as part of a chain/RunnableSequence. The Graph can also be a dependency of a RunnableLambda, but it has to be the actual compiled graph.

[BigLiao]

Indeed, it seems this way can not effectively store/restore the state of subgraphs.

[vbarda]

Hi folks! We recently launched full support for subgraphs -- would love if you tried it out and let us know if you're still running into any issues!

[yunhzou]

Hi vbarda, the visualization is still not working when subgraph is invoke/wrapped by a function that is assigned to the node.