pyserial: make serial.threaded.ReaderThread generic in the type of Protocol (#13425)

stubs/pyserial/serial/threaded/__init__.pyi

@@ -2,19 +2,22 @@ import threading
 from _typeshed import ReadableBuffer
 from collections.abc import Callable
 from types import TracebackType
+from typing import Generic, TypeVar
 from typing_extensions import Self
 
 from serial import Serial
 
+_P = TypeVar("_P", bound=Protocol, default="Protocol")  # noqa: Y020
+
 class Protocol:
-    def connection_made(self, transport: ReaderThread) -> None: ...
+    def connection_made(self, transport: ReaderThread[Self]) -> None: ...
     def data_received(self, data: bytes) -> None: ...
     def connection_lost(self, exc: BaseException | None) -> None: ...
 
 class Packetizer(Protocol):
     TERMINATOR: bytes
     buffer: bytearray
-    transport: ReaderThread | None
+    transport: ReaderThread[Self] | None
     def handle_packet(self, packet: bytes) -> None: ...
 
 class FramedPacket(Protocol):
@@ -22,7 +25,7 @@ class FramedPacket(Protocol):
     STOP: bytes
     packet: bytearray
     in_packet: bool
-    transport: ReaderThread | None
+    transport: ReaderThread[Self] | None
     def handle_packet(self, packet: bytes) -> None: ...
     def handle_out_of_packet_data(self, data: bytes) -> None: ...
 
@@ -32,17 +35,17 @@ class LineReader(Packetizer):
     def handle_line(self, line: str) -> None: ...
     def write_line(self, text: str) -> None: ...
 
-class ReaderThread(threading.Thread):
+class ReaderThread(threading.Thread, Generic[_P]):
     serial: Serial
-    protocol_factory: Callable[[], Protocol]
+    protocol_factory: Callable[[], _P]
     alive: bool
-    protocol: Protocol
-    def __init__(self, serial_instance: Serial, protocol_factory: Callable[[], Protocol]) -> None: ...
+    protocol: _P
+    def __init__(self, serial_instance: Serial, protocol_factory: Callable[[], _P]) -> None: ...
     def stop(self) -> None: ...
     def write(self, data: ReadableBuffer) -> int: ...
     def close(self) -> None: ...
-    def connect(self) -> tuple[Self, Protocol]: ...
-    def __enter__(self) -> Protocol: ...
+    def connect(self) -> tuple[Self, _P]: ...
+    def __enter__(self) -> _P: ...
     def __exit__(
         self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None, /
     ) -> None: ...