"Node" is unknown import symbol

Question

I installed mptt and created some categories and sub categories. Now I want to control under admin page

admin.py

from django.contrib import admin
from zummit.models import Product
from zummit.models import ProductImage
from mptt.admin import MPTTModelAdmin
from zummit.models import Node

admin.site.register(Product)
admin.site.register(Node, MPTTModelAdmin)

I am getting ""Node" is unknown import symbol" error for import Node area

views.py

class Category(MPTTModel):
    name = models.CharField(max_length=50, unique=True)
    parent = TreeForeignKey('self', on_delete=models.CASCADE, null=True, blank=True, related_name='children')

    class MPTTMeta:
        order_insertion_by = ['name']

What is the problem here?