code: protected boolean matchHeaderPattern(HttpMessage msg, String header, Pattern pattern) {
          if (msg.getResponseHeader().isEmpty()) {
              return false;
          }
  
          String val = msg.getResponseHeader().getHeader(header);
          if (val == null) {
              return false;
          }
  
          Matcher matcher = pattern.matcher(val);
          return matcher.find();
      }
docs: Check if the given pattern can be found in the header.
  
  @param msg the message that will be checked
  @param header the name of the header
  @param pattern the pattern that will be used
  @return true if the pattern can be found.