code: func substring_match_equal_func(model *C.GtkTreeModel,
  	column C.gint,
  	key *C.gchar,
  	iter *C.GtkTreeIter,
  	data C.gpointer) C.gboolean {
  
  	goModel := &TreeModel{glib.Take(unsafe.Pointer(model))}
  	goIter := &TreeIter{(C.GtkTreeIter)(*iter)}
  
  	value, err := goModel.GetValue(goIter, int(column))
  	if err != nil {
  		return gbool(true)
  	}
  
  	str, _ := value.GetString()
  	if str == "" {
  		return gbool(true)
  	}
  
  	subStr := C.GoString((*C.char)(key))
  	res := strings.Contains(str, subStr)
  	return gbool(!res)
  }
docs: //export substring_match_equal_func