code: public List<String> preview(int limit, boolean noHeaderLine) {
          E.illegalArgumentIf(limit < 1, "limit must be positive integer");
          return fetch(noHeaderLine ? 1 : 0, limit);
      }
docs: Returns first `limit` lines.
  
  @param limit
  the number of lines to be returned
  @param noHeaderLine
  if `false` then header line will be excluded in the return list
  @return the first `limit` lines.