code: protected ListIterator<Header> getHeaders(String header) {
      if (message == null) {
        return Collections.<Header>emptyList().listIterator();
      }
  
      return message.getHeaders(header);
    }
docs: This method is FOR SIPUNIT INTERNAL USE ONLY. It requires knowledge of JAIN SIP API. Used by
  SipTestCase/SipAssert.
  
  <p>
  Obtains a ListIterator over all the headers with the specified name in this message. The order
  of the items returned is the same as the order in which they appeared in the message.
  
  @param header the string identifying the header as specified in RFC-3261.
  @return the ListIterator over all the Headers of the specified name in the Message, this method
  returns an empty ListIterator if no Headers exist of this header type.