I'm trying to add a personal label to a Confluence page via the REST API. My `/content/{0}/label` POST works for "regular" labels, but when I try to prefix my label with `my:`, which is what makes the label a personal label, the API returns http 500. Is this supposed to work and is broken, or is it no supported? Perhaps I'm not quoting the colon (:) properly. Anyone have a working example? I'm using Python 2.7 with the requests and json modules