code: @Override
  	public  T listGetPrevious(final T currentElement) {
  
  		Relation<T, T, OneStartpoint<T>, OneEndpoint<T>> prevRel = currentElement.getIncomingRelationship(getSiblingLinkType());
  		if (prevRel != null) {
  
  			return (T)prevRel.getSourceNode();
  		}
  
  		return null;
  	}
docs: Returns the predecessor of the given element in the list structure
  defined by this LinkedListManager.
  
  @param currentElement
  @return previous element