def init(cls, typ, class2type):
        """
        Defines custom fields in the value factory so that the importer can find them
        @param typ
        @param class2type
        """
        field = typ.getField(cls.FIELD_NAME)
        class2type.put( StrStrHashMap , typ )
        typ.setComponentType( StrStrHashMap )
        typ.setImportExportHelper( StrStrHashMapSerializer(typ, field))
        typ.putValidator(field, Validator_object.get(1))
        typ.lock()
def _get_selected_path(self):
        """
        Helper function to get the selected path

        @return Gtk.TreePath : returns exactly one path for the selected object
                               or None
        """
        selection = self.get_selection()
        if selection:
            model, selected_paths = self.get_selection().get_selected_rows()
            if selected_paths:
                return selected_paths[0]
        return None