fix method access in Trainer APIs

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/proxy/branches/version-2.0-work@1519761 13f79535-47bb-0310-9956-ffa450edef68
allow any matching Trainer

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/proxy/branches/version-2.0-work@1519762 13f79535-47bb-0310-9956-ffa450edef68