Add a TODO comment.

ericsnowcurrently · ericsnowcurrently · commit 60a78ab1e360 · 2022-12-02T10:41:46.000-07:00
diff --git a/Modules/_xxsubinterpretersmodule.c b/Modules/_xxsubinterpretersmodule.c
@@ -6,6 +6,7 @@
 #endif
 
 #include "Python.h"
+// XXX This module should not rely on internal API.
 #include "pycore_frame.h"
 #include "pycore_pystate.h"       // _PyThreadState_GET()
 #include "pycore_interpreteridobject.h"
