How to use the pgspecial.open_external_editor function in pgspecial

:param text: Document
        :return: Document
        """
        editor_command = special.editor_command(text)
        while editor_command:
            if editor_command == "\\e":
                filename = special.get_filename(text)
                query = special.get_editor_query(text) or self.get_last_query()
            else:  # \ev or \ef
                filename = None
                spec = text.split()[1]
                if editor_command == "\\ev":
                    query = self.pgexecute.view_definition(spec)
                elif editor_command == "\\ef":
                    query = self.pgexecute.function_definition(spec)
            sql, message = special.open_external_editor(filename, sql=query)
            if message:
                # Something went wrong. Raise an exception and bail.
                raise RuntimeError(message)
            while True:
                try:
                    text = self.prompt_app.prompt(default=sql)
                    break
                except KeyboardInterrupt:
                    sql = ""

            editor_command = special.editor_command(text)
        return text

"select * from \e" to edit it in vim, then come
        back to the prompt with the edited query "select * from
        blah where q = 'abc'\e" to edit it again.
        :param cli: CommandLineInterface
        :param document: Document
        :return: Document
        """
        # FIXME: using application.pre_run_callables like this here is not the best solution.
        # It's internal api of prompt_toolkit that may change. This was added to fix #668.
        # We may find a better way to do it in the future.
        saved_callables = cli.application.pre_run_callables
        while special.editor_command(document.text):
            filename = special.get_filename(document.text)
            query = (special.get_editor_query(document.text) or
                     self.get_last_query())
            sql, message = special.open_external_editor(filename, sql=query)
            if message:
                # Something went wrong. Raise an exception and bail.
                raise RuntimeError(message)
            cli.current_buffer.document = Document(sql, cursor_position=len(sql))
            cli.application.pre_run_callables = []
            document = cli.run()
            continue
        cli.application.pre_run_callables = saved_callables
        return document