admin.py

from django.contrib import admin
from django import forms
from models import *

from filters import CategoryFilterSpec
from django.contrib.admin.filterspecs import FilterSpec

def test_f(f):
    return getattr(f, 'name')=='parent' and f.rel.to == Category

FilterSpec.filter_specs.insert(0, (test_f, CategoryFilterSpec))

class TagAdmin(admin.ModelAdmin):
#    form    = TagAdminForm
    list_display = ( 'slug', 'parent')
    list_filter = ( 'parent', )


admin.site.register(Category)
admin.site.register(Tag, TagAdmin)
admin.site.register(TestModel)