Revert "refactor: reorganize message handling for better type safety and clar…" (#282)

This reverts commit 9d0f2daddb.

src/mcp/client/sse.py

@@ -6,16 +6,10 @@ from urllib.parse import urljoin, urlparse
 import anyio
 import httpx
 from anyio.abc import TaskStatus
+from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
 from httpx_sse import aconnect_sse
 
 import mcp.types as types
-from mcp.shared.session import (
-    ReadStream,
-    ReadStreamWriter,
-    WriteStream,
-    WriteStreamReader,
-)
-from mcp.types import MessageFrame
 
 logger = logging.getLogger(__name__)
 
@@ -37,11 +31,11 @@ async def sse_client(
     `sse_read_timeout` determines how long (in seconds) the client will wait for a new
     event before disconnecting. All other HTTP operations are controlled by `timeout`.
     """
-    read_stream: ReadStream
-    read_stream_writer: ReadStreamWriter
+    read_stream: MemoryObjectReceiveStream[types.JSONRPCMessage | Exception]
+    read_stream_writer: MemoryObjectSendStream[types.JSONRPCMessage | Exception]
 
-    write_stream: WriteStream
-    write_stream_reader: WriteStreamReader
+    write_stream: MemoryObjectSendStream[types.JSONRPCMessage]
+    write_stream_reader: MemoryObjectReceiveStream[types.JSONRPCMessage]
 
     read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
     write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
@@ -90,11 +84,8 @@ async def sse_client(
 
                                     case "message":
                                         try:
-                                            message = MessageFrame(
-                                                message=types.JSONRPCMessage.model_validate_json(  # noqa: E501
-                                                    sse.data
-                                                ),
-                                                raw=sse,
+                                            message = types.JSONRPCMessage.model_validate_json(  # noqa: E501
+                                                sse.data
                                             )
                                             logger.debug(
                                                 f"Received server message: {message}"