code: public Iterator<MobicentsSipSession> getDerivedSipSessions() {
  		if(derivedSipSessions != null) {
  			return derivedSipSessions.values().iterator();
  		}
  		return new HashMap<String, MobicentsSipSession>().values().iterator();
  	}
docs: /*
  (non-Javadoc)
  @see org.mobicents.servlet.sip.core.session.MobicentsSipSession#getDerivedSipSessions()