In `@crates/derive-impl/src/pyclass.rs`:
- Around line 588-595: The code currently allows `clear` to be true while
`traverse` is absent which leaves `HAS_TRAVERSE` false and makes GC traversal a
no-op; update the logic around `has_traverse` and `has_clear` in the block using
`class_meta.inner()._has_key` and `class_meta.inner()._bool` to validate that if
`clear` is present and true then `traverse` must also be present (or return an
error) — e.g. after computing `has_clear` check `if has_clear && !has_traverse {
return Err(...) }` referencing the same symbols (`has_traverse`, `has_clear`,
`class_meta.inner()._has_key`, `_bool`, `HAS_TRAVERSE`) so the parser fails the
derive when `clear` is enabled without `traverse`.
- Around line 643-644: The generated signature for try_traverse is using
::rustpython_vm::object::TraverseFn without its required lifetime; update the
generated code so all uses of TraverseFn include the lifetime parameter (e.g.
TraverseFn<'a>) and propagate that 'a into the impl/generics for try_traverse
and any surrounding impl blocks where tracer_fn is referenced (look for the
try_traverse function and references to ::rustpython_vm::object::TraverseFn and
add the 'a lifetime consistently).

In `@crates/vm/src/builtins/function.rs`:
- Around line 54-58: The traversal currently grabs blocking locks (e.g.
self.type_params.lock().traverse(...), self.annotations.lock().traverse(...),
self.module.lock().traverse(...), self.doc.lock().traverse(...)) which can block
the GC and deadlock; instead call the Traverse implementation on the PyMutex
fields directly (use the PyMutex's non-blocking traverse method or
try_lock-based impl) — replace usages of .lock().traverse(tracer_fn) with the
PyMutex/field's traverse(tracer_fn) so traversal uses the non-blocking path for
type_params, annotations, module and doc.