docs: public String timestamp() {
          float totalSeconds = this.length();
          float second = totalSeconds % 60;
          int minute = (int) totalSeconds / 60 % 60;
          int hour = (int) (totalSeconds / 3600);
  
          StringBuilder sb = new StringBuilder();
          if (hour > 0) {
              sb.append(hour + ":");
          }
          if (minute > 0) {
              sb.append(minute + ":");
          }
          sb.append(second);
  
          return sb.toString();
      }