Fix type hint for packet, is_annexb

Author: WyattBlue

av/packet.pyi

@@ -1,5 +1,6 @@
+from collections.abc import Buffer
 from fractions import Fraction
-from typing import Buffer, Iterator
+from typing import Iterator
 
 from av.subtitles.subtitle import SubtitleSet
 
@@ -22,3 +23,4 @@ class Packet(Buffer):
 
     def __init__(self, input: int | bytes | None = None) -> None: ...
     def decode(self) -> Iterator[SubtitleSet]: ...
+    def __buffer__(self, arg1) -> memoryview: ...

tests/test_bitstream.py

@@ -5,7 +5,10 @@
 from .common import TestCase, fate_suite
 
 
-def is_annexb(packet: Packet) -> bool:
+def is_annexb(packet: Packet | bytes | None) -> bool:
+    if packet is None:
+        return False
+
     data = bytes(packet)
     return data[:3] == b"\0\0\x01" or data[:4] == b"\0\0\0\x01"