How to use the river.config.app_config.CONTENT_TYPE_CLASS.objects.get_for_model function in river

def filter(self, *args, **kwarg):
        workflow_object = kwarg.pop('workflow_object', None)
        if workflow_object:
            kwarg['content_type'] = app_config.CONTENT_TYPE_CLASS.objects.get_for_model(workflow_object)
            kwarg['object_id'] = workflow_object.pk

        return super(TransitionApprovalManager, self).filter(*args, **kwarg)

def __init__(self, workflow_object, field_name):
        self.class_workflow = getattr(workflow_object.__class__.river, field_name)
        self.workflow_object = workflow_object
        self.content_type = app_config.CONTENT_TYPE_CLASS.objects.get_for_model(self.workflow_object)
        self.field_name = field_name
        self.workflow = Workflow.objects.filter(content_type=self.content_type, field_name=self.field_name).first()
        self.initialized = False

def init_proceedings(workflow_object):

        content_type = app_config.CONTENT_TYPE_CLASS.objects.get_for_model(workflow_object)
        for proceeding_meta in ProceedingMeta.objects.filter(content_type=content_type):
            proceeding, created = Proceeding.objects.update_or_create(
                meta=proceeding_meta,
                workflow_object=workflow_object,
                defaults={
                    'order': proceeding_meta.order,
                    'status': PENDING,
                }
            )
            proceeding.permissions.add(*proceeding_meta.permissions.all())
            proceeding.groups.add(*proceeding_meta.groups.all())

        workflow_object.save()
        LOGGER.debug("Proceedings are initialized for workflow object %s" % workflow_object)

def update_or_create(self, *args, **kwarg):
        workflow_object = kwarg.pop('workflow_object', None)
        if workflow_object:
            kwarg['content_type'] = app_config.CONTENT_TYPE_CLASS.objects.get_for_model(workflow_object)
            kwarg['object_id'] = workflow_object.pk

        return super(TransitionApprovalManager, self).update_or_create(*args, **kwarg)