    // from: https://en.wikipedia.org/w/index.php?title=YANG&oldid=792171830#Example
    module example-sports {

      namespace "http://example.com/example-sports";
      prefix sports;

      import ietf-yang-types { prefix yang; }

      typedef season {
        type string;
        description
          "The name of a sports season, including the type and the year, e.g,
           'Champions League 2014/2015'.";
      }

      container sports {
        config true;

        list person {
          key name;
          leaf name { type string; }
          leaf birthday { type yang:date-and-time; mandatory true; }
        }

        list team {
          key name;
          leaf name { type string; }
          list player {
            key "name season";
            unique number;
            leaf name { type leafref { path "/sports/person/name"; }  }
            leaf season { type season; }
            leaf number { type uint16; mandatory true; }
            leaf scores { type uint16; default 0; }
          }
        }
      }
    }