Replace unsafe call with safe methods

src/instrumentation.rs

@@ -1,5 +1,6 @@
 //! APIs wrapping the Python interpreter's instrumentation features.
 use crate::ffi;
+use crate::ffi_ptr_ext::FfiPtrExt;
 use crate::pyclass::boolean_struct::False;
 use crate::types::PyFrame;
 use crate::{Bound, PyAny, PyClass, PyObject, PyRefMut, PyResult, Python};
@@ -82,7 +83,7 @@ where
         // We borrow the object so we don't break reference counting.
         //
         // https://docs.python.org/3/c-api/init.html#c.Py_tracefunc
-        let frame = unsafe { PyObject::from_borrowed_ptr(py, frame) };
+        let frame = frame.assume_borrowed_unchecked(py).downcast_unchecked();
         let frame = frame.extract(py).unwrap();
 
         // Safety: