public override void Accept(StringExpression str)
 {
     str.VisitChildren(this);
     methodBuilder.EmitInstruction(str.Location, Opcode.LoadConst,
                                   methodBuilder.Module.DefineConstant(new IodineString(str.Value)));
     if (str.Children.Count != 0)
     {
         methodBuilder.EmitInstruction(str.Location, Opcode.LoadAttribute,
                                       methodBuilder.Module.DefineConstant(new IodineName("format")));
         methodBuilder.EmitInstruction(str.Location, Opcode.Invoke, str.Children.Count);
     }
 }