code: private List<List<Integer>> calcOrbits() {
  		int n = subunits.getSubunitCount();
  
  		List<List<Integer>> orbits = new ArrayList<List<Integer>>();
  		for (int i = 0; i < n; i++) {
  			orbits.add(Collections.singletonList(i));
  		}
  
  		return orbits;
  	}
docs: Returns a list of list of subunit ids that form an "orbit", i.e. they
  are transformed into each other during a rotation around the principal symmetry axis (z-axis)
  @return