error: __traverse__ may not take `Python`. Usually, an implementation of `__traverse__` should do nothing but calls to `visit.call`. Most importantly, safe access to the GIL is prohibited inside implementations of `__traverse__`, i.e. `Python::with_gil` will panic.
  --> tests/ui/traverse.rs:18:32
   |
18 |     fn __traverse__(&self, py: Python<'_>, visit: PyVisit<'_>) -> Result<(), PyTraverseError> {
   |                                ^^^^^^^^^^

error[E0308]: mismatched types
  --> tests/ui/traverse.rs:9:6
   |
8  |   #[pymethods]
   |   ------------ arguments to this function are incorrect
9  |   impl TraverseTriesToTakePyRef {
   |  ______^
10 | |     fn __traverse__(slf: PyRef<Self>, visit: PyVisit) {}
   | |___________________^ expected fn pointer, found fn item
   |
   = note: expected fn pointer `for<'a, 'b> fn(&'a TraverseTriesToTakePyRef, PyVisit<'b>) -> Result<(), PyTraverseError>`
                 found fn item `for<'a, 'b> fn(pyo3::PyRef<'a, TraverseTriesToTakePyRef, >, PyVisit<'b>) {TraverseTriesToTakePyRef::__traverse__}`
note: function defined here
  --> src/impl_/pymethods.rs
   |
   | pub unsafe fn _call_traverse<T>(
   |               ^^^^^^^^^^^^^^