public static String pformat(Collection<?> c) {
    if(c.size() == 0) return "[]";
    StringBuilder result = new StringBuilder("[");
    for(Object elem : c) {
      if(c.size() != 1)
        result.append("\n  ");
      result.append(elem);
    }
    if(c.size() != 1)
      result.append("\n");
    result.append("]");
    return result.toString();
  }