code: public void appendLine(Object... parts) {
      if (parts.length > 0) {
        sb.append(indent);
      }
      appendParts(parts);
      sb.append('\n');
    }
docs: Appends a line. The indent at the start is automatically added whenever the line is nonempty
  (nonzero number of params). The newline char at the end is always added.
  
  @param parts The parts that make up the line.