如何命名模型的“预构建”对象的父类？

Question

I created a generator of the model of the application using some algorithms, it generates all the classes like:

Obj1 {
   // attrs...
   // methods (gets-sets)...
}

Obj2 {
   // attrs...
   // methods (gets-sets)..
}

...

I want to add new attributes and methods to that generated code, but it's complicated. To accomplish that, I created an alternate file with the same name of the object file name, and when the generator runs, it will take that files to append it to the classes, that's like this:

ObjN {
   // attrs...
   // methods (gets-sets)...
   require( "more-methods-and-attributes-for-objN.php" );
}

The problem with this is when I'm programming new features for that classes I need to work with plain text in that files (is very hard). Now I have the idea that is better to work with inheritance of classes to solve this, but I don't know what name to put to the parent class or use packages?

Option1> With prefix parent class:

class prebuilt_Obj1 {
   // attrs...
   // methods (gets-sets)..
}

class Obj1 extends prebuilt_Obj1 {
   // my attrs
   // my methods (gets-sets)
}

Option2> With packages:

namespace model/core;
class Obj1 {
   // attrs...
   // methods (gets-sets)..
}

namespace model;
use model/core/Obj1;
class Obj1 extends ¿Obj1? { //oops
   // my attrs
   // my methods (gets-sets)
}

¿What do you recommend?