There can be many proxies to a frame

pep-0558.rst

@@ -321,7 +321,7 @@ same internal snapshot storage.
 Only storing the internal mapping on the frame rather than storing an instance
 of the proxy type also avoids creating a reference cycle from the frame back to
 itself, so the frame will only be kept alive if another object retains a
-reference to the proxy.
+reference to a proxy instance.
 
 ``__getitem__`` operations on the proxy will read directly from the stored
 snapshot.