What is significnce of getPreAuthenticatedKeys function in SessionManager class

Hello

I am using openfire 3.6.4 and I want to know about the getPreAuthenticatedKeys function of the SessionManger, it is returning the keys created by the openfire to name a pre-authenticated session, why this function is added to library as I can not use this key for any reason as I can not find the user linked with this key, please suggest how these keys can be used.