code: @Override
      DeviceProxy get_device_i(int i) {
  	synchronized (this) {
  	    DeviceProxy dp = null;
  	    final Iterator it = elements.iterator();
  	    while (dp == null && it.hasNext()) {
  		final GroupElement e = (GroupElement) it.next();
  		dp = e.get_device_i(i--);
  	    }
  	    return dp;
  	}
      }
docs: Returns the <i>th device in the hierarchy - access limited to package
  Group