code: public String getLogDirectoryName(long timestamp, String pid, String label) {
          if (pid == null || pid.isEmpty()) {
              throw new IllegalArgumentException("pid cannot be empty");
          }
  
          StringBuilder sb = new StringBuilder();
          if (timestamp > 0) {
              sb.append(timestamp).append(TIMESEPARATOR);
          }
  
          sb.append(pid);
  
          if (label != null && !label.trim().isEmpty()) {
              sb.append(LABELSEPARATOR).append(label);
          }
  
          return sb.toString();
      }
docs: returns sub-directory name to be used for instances and sub-processes
  
  @param timestamp time of the instance start. It should be negative for sub-processes
  @param pid process Id of the instance or sub-process. It cannot be null or empty.
  @param label additional identification to use on the sub-directory.
  @return string representing requested sub-directory.