<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def requests_for_variant(self, request, variant_id=None):
 """Get all the requests for a single variant """

        requests = ProductRequest.objects.filter(variant__id=variant_id)
        serializer = self.serializer_class(requests, many=True)
        return Response(data=serializer.data, status=status.HTTP_200_OK)