"getattr(): attribute name must be string" in django rest framework

Question

There is an error "getattr(): attribute name must be string", I don't know how to solve this,

views.py:

class VideoViewset(ResponseViewMixin, mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet):

    def post(self, request, *args, **kwargs):
        try:
            serializer = VideoSerializers(data=request.data)
            if not serializer.is_valid():
                return self.jp_error_response('HTTP_400_BAD_REQUEST', self.error_msg_list(serializer.errors))
            serializer.save()
            return self.jp_response(s_code='HTTP_201_CREATED', data={'video': serializer.data})
        except Exception as e:
            print(e)
            return self.jp_error_response('HTTP_500_INTERNAL_SERVER_ERROR', 'EXCEPTION', [str(e), ])

serializers.py:

class VideoSerializers(serializers.ModelSerializer):
    class Meta:
        model = Video
        fields = ('video_type', 'relevance', 'difficulty', 'category', 'sub_category')

models.py:

class Video(BaseModel, Timestamps, SoftDelete):
    relevance_difficulty_choices = (
        ('low', 'Low'),
        ('medium', 'Medium'),
        ('high', 'High')
    )

    video_type_choices = (
        ('micro', 'Micro'),
        ('mini', 'Mini'),
        ('grand', 'Grand')
    )

    create_date = models.DateTimeField(auto_now_add=True, null=True)
    video_type = models.CharField(max_length=50, choices=video_type_choices, null=False)
    relevance = models.CharField(max_length=50, choices=relevance_difficulty_choices, null=False)

    difficulty = models.CharField(max_length=50, choices=relevance_difficulty_choices, null=False)
    category = models.CharField(max_length=254, null=False, blank=False)
    sub_category = models.CharField(max_length=254, null=False, blank=False)
    
    created_by = models.ForeignKey(Employee, null=True, on_delete=models.CASCADE)
    contributer = models.CharField(max_length=254, null=False)
    file_url = models.CharField(max_length=254, null=True, blank=False)

urls.py:

    router = routers.SimpleRouter(trailing_slash=False)
    router.register(r'categories', VideoCategoryViewSet, 'all-video-categories')
    router.register(r'search', VideoListViewset, 'search')
    router.register(r'video-add', VideoViewset, 'video-add')

This is my traceback:

 System check identified no issues (0 silenced).
 April 01, 2021 - 12:06:22
 Django version 3.1.3, using settings 'main.settings'
 Starting development server at http://0.0.0.0:8000/
 Quit the server with CONTROL-C.
 getattr(): attribute name must be string
 Internal Server Error: /api/e/video/video-add
"POST /api/e/video/video-add HTTP/1.1" 500 115
getattr(): attribute name must be string
Internal Server Error: /api/e/video/video-add
"POST /api/e/video/video-add HTTP/1.1" 500 115
getattr(): attribute name must be string
Internal Server Error: /api/e/video/video-add

i am beginer in django,What's I am doing wrong? here using postman to check,which showing the above error.