Retrieve guilds using after parameter.

async def _retrieve_guilds_after_strategy(self, retrieve):
        """Retrieve guilds using after parameter."""
        after = self.after.id if self.after else None
        data = await self.get_guilds(retrieve, after=after)
        if len(data):
            if self.limit is not None:
                self.limit -= retrieve
            self.after = Object(id=int(data[0]['id']))
        return data