rxgroups/src/main/java/com/airbnb/rxgroups/ObservableGroup.java
void destroy() {
    destroyed = true;

    for (Map<String, ManagedObservable<?>> observableMap : groupMap.values()) {
      for (ManagedObservable<?> managedObservable : observableMap.values()) {
        managedObservable.cancel();
      }
      observableMap.clear();
    }
    groupMap.clear();
  }
void destroy() {
    destroyed = true;

    for (Map<String, ManagedObservable<?>> observableMap : groupMap.values()) {
      for (ManagedObservable<?> managedObservable : observableMap.values()) {
        managedObservable.cancel();
      }
      observableMap.clear();
    }
    groupMap.clear();
  }
Cancels all subscriptions and releases references to Observables and Observers. No more
Observables can be added to this group after it has been destroyed and it becomes unusable.