@NotNull
  public String concatTrimmedLines(@NotNull String separator) {
    final StringBuilder b = new StringBuilder();
    List<Substring> lines = splitLines();
    final int n = lines.size();
    for (int i = 0; i < n; i++) {
      b.append(lines.get(i).trim().toString());
      if (i < n - 1) {
        b.append(separator);
      }
    }
    return b.toString();
  }
@NotNull
  public String concatTrimmedLines(@NotNull String separator)