module syslog1 {
    yang-version 1;
    namespace "http://huawei1.com";
    prefix "sys1";

    import "syslog2" {
       prefix "sys2";
    }

    identity ipv4-address-family {
       base sys2:ref-address-family;
    }

    identity ipv6-address-family {
       base sys2:ref-address-family;
    }

    leaf tunnel {
        type identityref {
            base sys2:ref-address-family;
        }
    }

    leaf-list network-ref {
        type identityref {
            base sys2:ref-address-family;
        }
    }

}