public override void Visit(ISimpleTerm node)
        {
            if (node.Source != null)
            {
                node.Source.AcceptVisitor(this);
            }

            var term = node.Term.Trim();

            if (term.IndexOf(' ') != -1)
            {
                term = string.Format("\"{0}\"", term);
            }

            builder.Append(term);
        }
 public override void Visit(ISimpleTerm node)
 {
     throw new NotSupportedException();
 }
 public abstract void Visit(ISimpleTerm node);