Fix some minor typing issues

discord/player.py

@@ -151,7 +151,7 @@ class FFmpegAudio(AudioSource):
 
         self._process: subprocess.Popen = self._spawn_process(args, **kwargs)
         self._stdout: IO[bytes] = self._process.stdout  # type: ignore
-        self._stdin: Optional[IO[Bytes]] = None
+        self._stdin: Optional[IO[bytes]] = None
         self._pipe_thread: Optional[threading.Thread] = None
 
         if piping:
@@ -200,7 +200,7 @@ class FFmpegAudio(AudioSource):
                 self._process.terminate()
                 return
             try:
-                self._stdin.write(data)
+                self._stdin.write(data)  # type: ignore
             except Exception:
                 _log.debug('Write error for %s, this is probably not a problem', self, exc_info=True)
                 # at this point the source data is either exhausted or the process is fubar

discord/utils.py

@@ -187,7 +187,7 @@ def cached_slot_property(name: str) -> Callable[[Callable[[T], T_co]], CachedSlo
     return decorator
 
 
-class SequenceProxy(Generic[T_co], collections.abc.Sequence):
+class SequenceProxy(collections.abc.Sequence[T_co]):
     """Read-only proxy of a Sequence."""
 
     def __init__(self, proxied: Sequence[T_co]):
@@ -538,7 +538,7 @@ async def sane_wait_for(futures, *, timeout):
 def get_slots(cls: Type[Any]) -> Iterator[str]:
     for mro in reversed(cls.__mro__):
         try:
-            yield from mro.__slots__
+            yield from mro.__slots__  # type: ignore
         except AttributeError:
             continue