Define a compound analytic optical element made up of the combination of two or more individual optical elements.
This is just a convenience routine for semantic organization of optics. It can be useful to keep the list of optical planes cleaner, but you can certainly just add a whole bunch of planes all in a row without using this class to group them.
All optics should be of the same plane type (pupil or image); propagation between different optics contained inside one compound is not supported.
opticslist : list