code: public SipSession getCorrespondingSipSession(SipSession sipSession, String headerName) {
  		MobicentsSipSession correspondingSipSession = null;
  		if(headerName.equalsIgnoreCase(JoinHeader.NAME)) {
  			correspondingSipSession = joinSession.get(((MobicentsSipSession) sipSession).getKey());
  		} else if (headerName.equalsIgnoreCase(ReplacesHeader.NAME)) {
  			correspondingSipSession = replacesSession.get(((MobicentsSipSession) sipSession).getKey());
  		} else {
  			throw new IllegalArgumentException("headerName argument should either be one of Join or Replaces");
  		}
  		return correspondingSipSession;
  	}
docs: {@inheritDoc}