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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 async def export_invite_link(self):
 """ Use this method to export an invite link to a supergroup or a channel. The bot must be an administrator in the chat for this to work and must have the appropriate admin rights. Source: https://core.telegram.org/bots/api#exportchatinvitelink :return: Returns exported invite link as String on success. :rtype: :obj:`base.String` """

        if not self.invite_link:
            self.invite_link = await self.bot.export_chat_invite_link(self.id)

        return self.invite_link