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WeakFunctionProxy.__call__ checks self._self_instance (a weakref.ref)
for truthiness to detect expired references, but weakref.ref objects
are always truthy even after the referent is garbage collected.

When the instance dies but the function still lives (the usual case
since functions live in the class dict), _self_instance() returns
None, making the code fall into the unbound-function path. This calls
the original function without 'self', producing a confusing TypeError
instead of the expected ReferenceError.

Add an explicit check: if _self_instance was set (bound method) but
the dereferenced value is None, raise ReferenceError directly.

ObjectProxy.__setattr__ has special handling for both __qualname__
and __annotations__, forwarding them to both the proxy and the
wrapped object. However, __delattr__ only handles __qualname__ and
misses __annotations__, so deleting annotations on the proxy doesn't
propagate to the wrapped object.

This adds the missing __annotations__ branch to __delattr__ to match
the behavior of __setattr__.

…stance

Raise ReferenceError when bound method instance is garbage collected

Fix ObjectProxy.__delattr__ missing __annotations__ special case