fix: make echo work better

Signed-off-by: Chojan Shang <chojan.shang@vesoft.com>

Author: Chojan Shang

examples/echo_agent.py

@@ -1,13 +1,31 @@
 import asyncio
-
-from acp import Agent, AgentSideConnection, PromptRequest, PromptResponse, SessionNotification, stdio_streams
+from uuid import uuid4
+
+from acp import (
+    Agent,
+    AgentSideConnection,
+    InitializeRequest,
+    InitializeResponse,
+    NewSessionRequest,
+    NewSessionResponse,
+    PromptRequest,
+    PromptResponse,
+    SessionNotification,
+    stdio_streams,
+)
 from acp.schema import AgentMessageChunk, TextContentBlock
 
 
 class EchoAgent(Agent):
     def __init__(self, conn):
         self._conn = conn
 
+    async def initialize(self, params: InitializeRequest) -> InitializeResponse:
+        return InitializeResponse(protocolVersion=params.protocolVersion)
+
+    async def newSession(self, params: NewSessionRequest) -> NewSessionResponse:
+        return NewSessionResponse(sessionId=uuid4().hex)
+
     async def prompt(self, params: PromptRequest) -> PromptResponse:
         for block in params.prompt:
             text = getattr(block, "text", "")