fix: MCP calling node error #3752

Author: shaohuzhang1

apps/application/flow/step_node/mcp_node/impl/base_mcp_node.py

@@ -4,7 +4,6 @@
 from typing import List
 
 from langchain_mcp_adapters.client import MultiServerMCPClient
-from langchain_mcp_adapters.sessions import create_session
 
 from application.flow.i_step_node import NodeResult
 from application.flow.step_node.mcp_node.i_mcp_node import IMcpNode
@@ -25,7 +24,7 @@ def execute(self, mcp_servers, mcp_server, mcp_tool, tool_params, **kwargs) -> N
 
         async def call_tool(t, a):
             client = MultiServerMCPClient(servers)
-            async with create_session(client.connections[mcp_server]) as s:
+            async with client.session(mcp_server) as s:
                 return await s.call_tool(t, a)
 
         res = asyncio.run(call_tool(mcp_tool, params))