Django 1.7, 1.8 - queryset.extra is deprecated, how to do group by on datetime with date

In Django 1.5/1.6 version -

signup_count = list(User.objects.filter(
            profile__user_type='learner').order_by(
                '-id').extra({
                             'date_only': "date(date_joined)"}).values(
                                 'date_only').annotate(
                                     signup_count=Count('id'))[:40])

It used to return list with
[{ 'date_only': , 'signup_count': }]

Now, as the extra is deprecated in newer version of Django, here the work around to get the same -

from django.db.models.expressions import Func

# Create custom sql function
class ExtractDateFunction(Func):

    function = "DATE"

signup_signup = list(User.objects.filter(
            profile__user_type='learner').order_by('-id')annotate(
date_only=ExtractDateFunction("date_joined")).values(
'date_only').annotate(
teacher_count=Count('id'))[:40])

This should give you the same results as before.