langchian事件

要么手写个迭代器自定义event，要摸使用langchain自带的事件
        initial_state = {
            "messages": chat_history or [] + [_HumanMessage(content=message)],
            "user_input": message,
            "session_id": session_id,
            "iteration": 0,
        }

        config = {"configurable": {"thread_id": session_id}}

        async for event in self.graph.astream_events(
            initial_state, config=config, version="v2"
        ):
        你的业务



from langchain_core.runnables import RunnableConfig as _RunnableConfig
from datetime import datetime

from ..state import searchState as _searchState
from ...schemas.agents.base_dsl import BaseDSL as _BaseDSL
from ...agents.search_node_agent import search_node_agent as _search_node_agent


async def search_nodes_node(
    state: _searchState,
    config: _RunnableConfig,
) -> _searchState:
    """Search nodes in the workflow graph."""

    # 获取回调管理器
    callbacks = config.get("callbacks")
    
    # 手动发送CPDD开始事件
    if callbacks:
        cpdd_start_event = {
            "event": "cpdd",
            "cpdd": "开始搜索可用节点",
            "node_type": "search_nodes",
            "status": "start",
            "timestamp": datetime.now().isoformat(),
            "data": {"query": state["messages"][-1].content}
        }
        
        # 使用特殊的序列化标识来标记这是CPDD事件
        await callbacks.on_chain_start(
            serialized={"name": "cpdd_event", "event_type": "cpdd"},
            inputs=cpdd_start_event
        )

    query = state["messages"][-1].content
    response = _search_node_agent.invoke(
        {"messages": [{"role": "user", "content": query}]}
    )["structured_response"]

    # 手动发送CPDD完成事件
    if callbacks:
        cpdd_end_event = {
            "event": "cpdd",
            "cpdd": "节点搜索完成",
            "node_type": "search_nodes", 
            "status": "end",
            "timestamp": datetime.now().isoformat(),
            "data": {
                "nodes_found": len(response.nodes_list),
                "edges_found": len(response.edges_list)
            }
        }
        
        await callbacks.on_chain_end(outputs=cpdd_end_event)

    state["nodes_list"] = response.nodes_list
    state["edges_list"] = response.edges_list
    state["dsl"] = _BaseDSL(nodes=[], edges=[])
    state['dsl_json'] = state['dsl'].model_dump_json(indent=2, exclude_none=True, ensure_ascii=False)

    return state