code: public Set<Class<?>> getAllGroupsAndSequences() {
      final Set<Class<?>> allGroups = new HashSet<>();
      for (final Map.Entry<Class<?>, Set<Class<?>>> entry : inheritanceMapping.entrySet()) {
        allGroups.add(entry.getKey());
        allGroups.addAll(entry.getValue());
      }
      allGroups.addAll(sequenceMapping.keySet());
      return allGroups;
    }
docs: Recursively gets all of the groups and sequence groups in the map (children and parents alike)
  in one flat set.
  
  @return set of groups