PYTHON-5543 Fix asyncio import

- Import and use BaseProtocol instead of Protocal in
  PyMongoBaseProtocoal implementation. Resolves issue with instance type
  check in uvloop that prevents correct buffered config from being set.

Author: aclark4life

doc/changelog.rst

@@ -1,6 +1,14 @@
 Changelog
 =========
 
+Changes in Version 4.15.1 (XXXX/XX/XX)
+--------------------------------------
+
+Version 4.15.1 is a bug fix release.
+
+- Fixed a bug in ``MongoClient.network_layer`` and ``AsyncMongoClient.network_layer``
+  that could cause an ``TimeoutError`` when connecting to servers.
+
 Changes in Version 4.15.0 (2025/09/10)
 --------------------------------------
 

pymongo/network_layer.py

@@ -22,7 +22,7 @@
 import struct
 import sys
 import time
-from asyncio import BaseTransport, BufferedProtocol, Future, Protocol, Transport
+from asyncio import BaseProtocol, BaseTransport, BufferedProtocol, Future, Transport
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -250,7 +250,7 @@ def recv_into(self, buffer: bytes | memoryview) -> int:
         return self.conn.recv_into(buffer)
 
 
-class PyMongoBaseProtocol(Protocol):
+class PyMongoBaseProtocol(BaseProtocol):
     def __init__(self, timeout: Optional[float] = None):
         self.transport: Transport = None  # type: ignore[assignment]
         self._timeout = timeout