chore: import upstream snapshot with attribution

tests/langgraph/sample_code/langgraph_diy.py

@@ -0,0 +1,46 @@
+# Sample code that contains custom python nodes
+from typing import Annotated, Sequence, TypedDict
+
+from langchain_core.messages import BaseMessage
+from langchain_openai import ChatOpenAI
+from langgraph.graph import END, START, StateGraph
+from langgraph.graph.message import add_messages
+
+import mlflow
+
+
+def generate(state):
+    messages = state["messages"]
+    llm = ChatOpenAI()
+    response = llm.invoke(messages[-1].content)
+    return {"messages": response}
+
+
+def should_continue(state):
+    if len(state["messages"]) > 3:
+        return "no"
+    else:
+        return "yes"
+
+
+class AgentState(TypedDict):
+    # The add_messages function defines how an update should be processed
+    # Default is to replace. add_messages says "append"
+    messages: Annotated[Sequence[BaseMessage], add_messages]
+
+
+workflow = StateGraph(AgentState)
+workflow.add_node("generate", generate)
+workflow.add_edge(START, "generate")
+workflow.add_conditional_edges(
+    "generate",
+    should_continue,
+    {
+        "yes": "generate",
+        "no": END,
+    },
+)
+
+graph = workflow.compile()
+
+mlflow.models.set_model(graph)