code: public Set<String> getExpand()
  	{
  		List<String> values = parameters.get(WQUriControlField.EXPAND.getName());
  
  		if (values == null || values.isEmpty())
  			return Collections.singleton("all");
  		else
  			return new HashSet<>(values);
  	}
docs: Retrieve the {@link WQUriControlField#EXPAND} parameter as a Set (or "all" if none is defined)
  
  @return