module mod1 {
    prefix abc;
    namespace "urn:cesnet:mod1";

    grouping ssh {
        container ssh {
            leaf key { type string; }
            leaf user {
                type string {
                    pattern '[a-z0-9]';
                }
            }
            leaf is_valid {
                type boolean;
                default "false";
            }
        }
    }

    container server {
        uses ssh {
            refine ssh/ssh {        // unknown node
                description "test";
            }
        }
    }
}