@org.apache.thrift.annotation.Nullable
    public static _Fields findByThriftId(int fieldId) {
      switch(fieldId) {
        case 1: // TABLE
          return TABLE;
        case 2: // ROW
          return ROW;
        case 3: // COLUMNS
          return COLUMNS;
        case 4: // VALUES
          return VALUES;
        default:
          return null;
      }
    }
Find the _Fields constant that matches fieldId, or null if its not found.
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/generated/TAppend.java