code: private boolean isSessionFilename(String filename) {
          if (!StringUtils.hasText(filename)) {
              return false;
          }
          String[] parts = filename.split("_");
          // Need at least 2 parts for a valid filename
          return (parts.length >= 2);
      }
docs: Check if the filename matches our session pattern.
  
  @param filename the name of the file to checks
  @return true if pattern matches