code: public Set<String> getSubsystems() throws IOException, XMLStreamException {
          final Set<String> result = new HashSet<>();
          for (ConfigFile configFile : description.getConfig().getDomainConfigFiles()) {
              for (Map<String, SubsystemConfig> subsystems : configFile.getSubsystemConfigs(featurePackFile).values()) {
                  result.addAll(subsystems.keySet());
              }
          }
          for (ConfigFile configFile : description.getConfig().getStandaloneConfigFiles()) {
              for (Map<String, SubsystemConfig> subsystems : configFile.getSubsystemConfigs(featurePackFile).values()) {
                  result.addAll(subsystems.keySet());
              }
          }
          for (ConfigFile configFile : description.getConfig().getHostConfigFiles()) {
              for (Map<String, SubsystemConfig> subsystems : configFile.getSubsystemConfigs(featurePackFile).values()) {
                  result.addAll(subsystems.keySet());
              }
          }
          return result;
      }
docs: Retrieves all subsystems included in the feature pack config files.
  @return
  @throws IOException
  @throws XMLStreamException