      # In the general case they do not provide .remove() or .clear()
      # and cannot be arbitrarily set.
  
      # def test_reverse_foreign_key_update(self):
      #     data = {'id': 1, 'name': u'target-1', 'sources': [1]}
      #     instance = ForeignKeyTarget.objects.get(pk=1)
      #     serializer = ForeignKeyTargetSerializer(instance, data=data)
      #     self.assertTrue(serializer.is_valid())
      #     self.assertEquals(serializer.data, data)
      #     serializer.save()
 
</s> remove             {'id': 1, 'name': u'source-1', 'target': 2},
            {'id': 2, 'name': u'source-2', 'target': 1},
            {'id': 3, 'name': u'source-3', 'target': 1}
 </s> add             {'id': 1, 'name': 'source-1', 'target': 2},
            {'id': 2, 'name': 'source-2', 'target': 1},
            {'id': 3, 'name': 'source-3', 'target': 1} </s> remove         data = {'id': 1, 'name': u'target-1', 'sources': [1]}
 </s> add         data = {'id': 1, 'name': 'target-1', 'sources': [1]} </s> remove     #         {'id': 1, 'name': u'target-1', 'sources': [1]},
    #         {'id': 2, 'name': u'target-2', 'sources': []},
 </s> add     #         {'id': 1, 'name': 'target-1', 'sources': [1]},
    #         {'id': 2, 'name': 'target-2', 'sources': []}, </s> remove         data = {'id': 1, 'name': u'source-1', 'target': 2}
 </s> add         data = {'id': 1, 'name': 'source-1', 'target': 2} </s> remove         data = {'id': 1, 'name': u'source-1', 'targets': [1, 2, 3]}
 </s> add         data = {'id': 1, 'name': 'source-1', 'targets': [1, 2, 3]}
    #     data = {'id': 1, 'name': 'target-1', 'sources': [1]}
      # In the general case they do not provide .remove() or .clear()
      # and cannot be arbitrarily set.
  
      # def test_reverse_foreign_key_update(self):
    #     data = {'id': 1, 'name': 'target-1', 'sources': [1]}
      #     instance = ForeignKeyTarget.objects.get(pk=1)
      #     serializer = ForeignKeyTargetSerializer(instance, data=data)
      #     self.assertTrue(serializer.is_valid())
      #     self.assertEquals(serializer.data, data)
      #     serializer.save()
keep keep keep keep replace keep keep keep keep keep
 First passing test under p3k \o/ 
rest_framework/tests/pk_relations.py