Error

class NewDialog(Gtk.Dialog):
    __gtype_name__ = "NewDialog"

    def __new__(cls):
        """Special static method that's automatically called by Python when
        constructing a new instance of this class.

        Returns a fully instantiated NewDialog object.
        """
        builder = get_builder('NewDialog')
        new_object = builder.get_object('new_dialog')
        new_object.finish_initializing(builder)
        return new_object

    def finish_initializing(self,builder):
        """Called when we're finished initializing.

        finish_initalizing should be called after parsing the ui definition
        and creating a NewDialog object with it in order to
        finish initializing the start of the new NewDialog
        instance.
        """
        # Get a reference to the builder and set up the signals.
        self.builder = builder
        self.ui = builder.get_ui(self)