If you have Proxy references in a scene it can be tricky to find which ones are related.
string $allRefNodes = `getRelatedProxies($refNode)`; // if no proxies are found, an empty string is returned
// Mel procedure found in : <MAYA_LOCATION>/scripts/others/getRelatedProxies.mel
And to find the proxyManager node, use this:
string $proxyManager = `proxyManager($refNode)`;
// Mel procedure found in : <MAYA_LOCATION>/scripts/others/proxyUtils.mel
These procedures are shipped with Maya. Pythonites will need to transcribe these MEL procedures.