@org.apache.thrift.annotation.Nullable
    public static _Fields findByThriftId(int fieldId) {
      switch(fieldId) {
        case 1: // NODE_TYPE
          return NODE_TYPE;
        case 2: // ROOTS
          return ROOTS;
        case 3: // ADJACENCY_LIST
          return ADJACENCY_LIST;
        default:
          return null;
      }
    }
Find the _Fields constant that matches fieldId, or null if its not found.
ql/src/gen/thrift/gen-javabean/org/apache/hadoop/hive/ql/plan/api/Graph.java