On 3.13, Py_IsFinalizing is a supported API, and the private one is gone.

Author: jamadden

Diff for: src/greenlet/TThreadStateDestroy.cpp

@@ -103,7 +103,11 @@ struct ThreadState_DestroyNoGIL
         // segfault if we happen to get context switched, and maybe we should
         // just always implement our own AddPendingCall, but I'd like to see if
         // this works first
+#if GREENLET_PY313
+        if (Py_IsFinalizing()) {
+#else
         if (_Py_IsFinalizing()) {
+#endif
             fprintf(stderr,
                     "greenlet: WARNING: Interpreter is finalizing. Ignoring "
                     "call to Py_AddPendingCall; \n");