code: public Collection<Parameter<?>> getParameters() {
          if (_parameters == null) {
              return Collections.<Parameter<?>>emptyList();
          }
          
          return Collections.unmodifiableCollection(_parameters);
      }
docs: Returns all the {@link Parameter}s that are defined in this
  {@link WebSocketExtension}. An empty Collection is returned if there
  are no {@link Parameter}s defined.
  
  @return Collection of WebSocketExtensionParameters