How to use the tryton.common.message function in tryton

ids = self.ids_get()
        if not obj_id and ids and len(ids):
            obj_id = ids[0]
        if obj_id:
            ctx = self.context.copy()
            if 'active_ids' in ctx:
                del ctx['active_ids']
            if 'active_id' in ctx:
                del ctx['active_id']
            return Action.exec_keyword(keyword, self.window, {
                'model': self.model,
                'id': obj_id,
                'ids':ids,
                }, context=ctx, warning=warning)
        else:
            common.message(_('No record selected!'), self.window)
        return False

filename = filename.decode('utf-8')
            try:
                CONFIG['client.default_path'] = \
                       os.path.dirname(filename)
                CONFIG.save()
            except IOError:
                pass
        if response == gtk.RESPONSE_OK:
            if width and height and filename:
                if not filename.endswith('.png'):
                    filename = filename + '.png'
                try:
                    graph.export_png(filename, width, height)
                    break
                except MemoryError:
                    common.message(_('Image size too large!'), dia,
                            gtk.MESSAGE_ERROR)
        else:
            break
    parent.present()
    dia.destroy()
    return

def sig_test_expand_row(self, widget, iter, path):
        model = self.tree_res.view.get_model()
        iter_children = model.iter_children(iter)
        if iter_children and model.get(iter_children, 0)[0] in model.to_reload:
            hostname = rpc._SOCK.hostname
            port = rpc._SOCK.port
            while True:
                password = common.ask(_('Password:'), self.window,
                        visibility=False)
                if password is None:
                    return True
                res = rpc.login(rpc._USERNAME, password, hostname, port,
                        rpc._DATABASE)
                if res == -1:
                    common.message(_('Connection error!\n' \
                            'Unable to connect to the server!'), self.window)
                    return True
                if res < 0:
                    continue
                return False
        return False