public override void Visit(IProximityTerm node)
        {
            if (node.Source != null)
            {
                node.Source.AcceptVisitor(this);
            }
            int index = 0;

            foreach (var proximityOperand in node.Terms)
            {
                if (index != 0)
                {
                    builder.Append(" NEAR ");
                }
                proximityOperand.AcceptVisitor(this);
                index++;
            }
        }
 public override void Visit(IProximityTerm node)
 {
     throw new NotSupportedException();
 }
 public abstract void Visit(IProximityTerm node);