4.10.0rc1

Release 4.10.0rc1 (February 17, 2024)

• Add support for PEP 728, supporting the closed keyword argument and the
  special __extra_items__ key for TypedDict. Patch by Zixuan James Li.
• Add support for PEP 742, adding typing_extensions.TypeIs. Patch
  by Jelle Zijlstra.
• Drop runtime error when a read-only TypedDict item overrides a mutable
  one. Type checkers should still flag this as an error. Patch by Jelle
  Zijlstra.
• Speedup issubclass() checks against simple runtime-checkable protocols by
  around 6% (backporting python/cpython#112717, by Alex
  Waygood).
• Fix a regression in the implementation of protocols where typing.Protocol
  classes that were not marked as @runtime_checkable would be unnecessarily
  introspected, potentially causing exceptions to be raised if the protocol had
  problematic members. Patch by Alex Waygood, backporting
  python/cpython#113401.