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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 _retrieve_guilds_before_strategy(self, retrieve):
 """Retrieve guilds using before parameter."""

        before = self.before.id if self.before else None
        data = await self.get_guilds(retrieve, before=before)
        if len(data):
            if self.limit is not None:
                self.limit -= retrieve
            self.before = Object(id=int(data[-1]['id']))
        return data