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;
        }
    }
}