Add a manager to FlatPage model in Django

I'd like to extend the FlatPage model in Django so that I can implement searching within its field. That's what I've done:

models.py:

from django.db.models import Q
from django.contrib.flatpages.models import FlatPage

class FlatPageManager(models.Manager):
    def search(self, query=None):
        qs = self.get_queryset()
        if query is not None:
            or_lookup = (Q(title__icontains=query) |
                        Q(content__icontains=query)
                        )
            qs = qs.filter(or_lookup).distinct()
        return qs

class MyFlatPage(FlatPage):

    objects = FlatPageManager()

views.py:

class SearchView(ListView):
   [...]
    def get_context_data(self, *args, **kwargs):

        context['query'] = self.request.GET.get('q')
        return context

    def get_queryset(self):
        request = self.request
        query = request.GET.get('q', None)

        if query is not None:
            flatpage_results     = MyFlatPage.objects.search(query)


            qs = sorted(queryset_chain,
                        key=lambda instance: instance.pk,
                        reverse=True)
            return qs

The above search method works for other models I have, so it should also work for MyFlatPage. Nevertheless, I get no results coming from that query. Am I missing something?

Update 1

What is empty is the whole MyFlatPage list:

>>> MyFlatPage.objects.all()
<QuerySet []>

There is two common types for django models inheritance: the proxy-models and as a new models.

If you want to use FlatPage table as a table for new model - MyFlatPage you have to define MyFlatPage as a proxy one by adding proxy = True flag in Meta:

class MyFlatPage(FlatPage):
    class Meta:
        proxy = True

In other case you will have another table for MyFlatPage.