code: func (b *Builder) GetObject(name string) (glib.IObject, error) {
  	cstr := C.CString(name)
  	defer C.free(unsafe.Pointer(cstr))
  	c := C.gtk_builder_get_object(b.native(), (*C.gchar)(cstr))
  	if c == nil {
  		return nil, errors.New("object '" + name + "' not found")
  	}
  	obj, err := cast(c)
  	if err != nil {
  		return nil, err
  	}
  	return obj, nil
  }
docs: // GetObject is a wrapper around gtk_builder_get_object(). The returned result
  // is an IObject, so it will need to be type-asserted to the appropriate type before
  // being used. For example, to get an object and type assert it as a window:
  //
  //   obj, err := builder.GetObject("window")
  //   if err != nil {
  //       // object not found
  //       return
  //   }
  //   if w, ok := obj.(*gtk.Window); ok {
  //       // do stuff with w here
  //   } else {
  //       // not a *gtk.Window
  //   }
  //