public bool HasVariableBeenAssigned(string name)
            {
                Contract.Requires(name != null);

                if (assignedAssumptionVariables.Contains(name))
                {
                    return(true);
                }
                else if (ParentContext != null)
                {
                    return(ParentContext.HasVariableBeenAssigned(name));
                }
                else
                {
                    return(false);
                }
            }
        public bool HasVariableBeenAssigned(string name)
        {
            Contract.Requires(name != null);

            return(varContext.HasVariableBeenAssigned(name));
        }