public List<MFieldSchema> getCols() {
    if (columns != null) {
      return columns;
    }
    columns = new ArrayList<>();
    if (fields != null) {
      columns = fields.stream().map(column ->
              new MFieldSchema(column.getName(), column.getType(), column.getComment()))
          .collect(Collectors.toList());
    }
    return columns;
  }
MColumnDescriptor.
A wrapper around a list of columns.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/model/MColumnDescriptor.java