public void addInline(Op op, Connection connection) {
    List<Connection> list = inlineMap.get(op);
    if (list == null) {
      list = new ArrayList<>();
      list.add(connection);
      inlineMap.put(op, list);
    } else {
      list.add(connection);
    }
  }
@param indentFlag
@param tail
         help to generate correct indent with a specific tail
@return
common/src/java/org/apache/hadoop/hive/common/jsonexplain/DagJsonParser.java