* Removed the `get_object_borrowed`, `upgrade_borrowed`, `upgrade_borrowed_as`,
`upgrade_borrowed_as_unchecked`, `upgrade_borrowed_as_exact` methods of
`PyWeakref` and `PyWeakrefProxy`. These returned borrowed references to weakly
referenced data, and in principle if the GIL is released the last strong
reference could be released, allowing a possible use-after-free error. If you
are using these functions, you should change to the equivalent function that
returns a `Bound<'py, T>` reference.
