* _PyTuple_ITEMS() gives access to the tuple->ob_item field and cast the
  first argument to PyTupleObject*. This internal macro is only usable if
  Py_BUILD_CORE is defined.
* Replace &PyTuple_GET_ITEM(ob, 0) with _PyTuple_ITEMS(ob).
* Replace PyTuple_GET_ITEM(op, 1) with &_PyTuple_ITEMS(ob)[1].