public void accept(InteractionUnitVisitor visitor)
    {
        visitor.startVisit(this);
        for (InteractionUnit child : children)
        {
            child.accept(visitor);
        }
        visitor.endVisit(this);
    }
public void accept ( InteractionUnitVisitor visitor ) { visitor . startVisit ( this ) ; for ( InteractionUnit child : children ) { child . accept ( visitor ) ; } visitor . endVisit ( this ) ; }
------------------------------------------------------ visitor related