'Create a serializer with the given data and (if updating) instance,
ensure that it is valid, save the result, and return the full thread
data from the serializer.'

def save_and_reserialize(self, data, instance=None):

    serializer = ThreadSerializer(instance, data=data, partial=(instance is not None), context=get_context(self.course, self.request))
    self.assertTrue(serializer.is_valid())
    serializer.save()
    return serializer.data
