private DisjunctiveRefinement(DisjunctiveRefinement other, Dictionary <Variable, HashSet <Variable> > vars)
                    : this(other)
                {
                    Contract.Requires(other != null);

                    this.varsInAssignment = vars;
                }
 private DisjunctiveRefinement(DisjunctiveRefinement other)
     : base(other)
 {
 }