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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:

def get_queryset(self):
        '''
        If MultiTenantMiddleware is used, filter queryset by request.site_id
        '''
        queryset = super(PageList, self).get_queryset()
        if hasattr(self.request, 'site_id'):
            queryset = queryset.filter(site_id=self.request.site_id)
        return queryset