code: public List findEquivalenceClasses() {
          if (atomContainer == null) {
              return null;
          }
  
          List<IRingSet> equivalenceClasses = new ArrayList<IRingSet>();
          for (Object o : cycleBasis().equivalenceClasses()) {
              equivalenceClasses.add(toRingSet(atomContainer, (Collection) o));
          }
          return equivalenceClasses;
      }
docs: Finds the "interchangeability" equivalence classes.
  The interchangeability relation is described in [GLS00].
  
  @return      a List of RingSets containing the rings in an equivalence class