code: @SuppressWarnings("unchecked")
    public <T> @NonNull Collection<Collection<T>> components() {
      return (Collection<Collection<T>>) this.components;
    }
docs: Accesses the strongly connected components.
  
  <p>Only those components with two or more nodes blocks the process
  of topological sorting.</p>
  
  @param <T> the node type restored
  @return the strongly connected components