fix langgraph workflow

agent.py

@@ -62,20 +62,20 @@ def processor_node(state: MessagesState):
         return {"messages": response}
 
 def agent_graph():
-    builder = StateGraph(MessagesState)
+    workflow = StateGraph(MessagesState)
 
     ## Add nodes
-    builder.add_node("retriever_node", retriever_node)
-    builder.add_node("processor_node", processor_node)
-    builder.add_node("tools", ToolNode(tools))
+    workflow.add_node("retriever_node", retriever_node)
+    workflow.add_node("processor_node", processor_node)
+    workflow.add_node("tools", ToolNode(tools))
 
     ## Add edges
-    builder.add_edge(START, "retriever_node")
-    builder.add_edge("retriever_node", "processor_node")
-    builder.add_conditional_edges("processor_node", tools_condition)
-    builder.add_edge("tools", "processor_node")
+    workflow.add_edge(START, "retriever_node")
+    workflow.add_edge("retriever_node", "processor_node")
+    workflow.add_conditional_edges("processor_node", tools_condition)
+    workflow.add_edge("tools", "processor_node")
 
     # Compile graph
-    builder.compile()
+    graph = workflow.compile()
 
-    return builder
+    return graph