Account for shared keys in type's __sizeof__ (#13903).
diff --git a/Include/dictobject.h b/Include/dictobject.h
index 36048f6..d908524 100644
--- a/Include/dictobject.h
+++ b/Include/dictobject.h
@@ -75,6 +75,7 @@
PyAPI_FUNC(PyObject *) _PyDict_NewPresized(Py_ssize_t minused);
PyAPI_FUNC(void) _PyDict_MaybeUntrack(PyObject *mp);
PyAPI_FUNC(int) _PyDict_HasOnlyStringKeys(PyObject *mp);
+Py_ssize_t _PyDict_KeysSize(PyDictKeysObject *keys);
#define _PyDict_HasSplitTable(d) ((d)->ma_values != NULL)
PyAPI_FUNC(int) PyDict_ClearFreeList(void);