code: @Override
  	public boolean isUnknown(Object value)
  	{
  		return (value instanceof Set) 
  			? emptySetOrContainsOnlyUnknowns((Set)value) 
  				: emptySetOrContainsOnlyUnknowns(Collections.singleton(value));
  	}
docs: According the editor type, this methods checks if value equals
  to one of the unknown values defined under {@link org.biopax.paxtools.model.BioPAXElement}
  or is an empty set or set of "unknown" values.
  
  @param value the value to be checked if it is unknown
  @return true, if value equals to the predefined unknown value