Django filter F and functions of fields. Filter by comparison between fields with lookups

Question

models

from django.db import models
from django.utils import timezone
import datetime
class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')
    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now
    def __str__(self):
        return self.question_text
class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.FloatField(default=0)
    # ...
    def __str__(self):
        return self.choice_text

creation

#from polls.models import Choice, Question;from django.utils import timezone
#q = Question(question_text="What's new?", pub_date=timezone.now());q.add(Choice(choice_text='variant', votes=0),Choice(choice_text='Not much', votes=0),Choice(choice_text='Just hacking again', votes=0),Choice(choice_text='The sky', votes=0));q.save;q = Question(question_text="m?", pub_date=timezone.now());q.save
#q = Question(question_text="Third question", pub_date=timezone.now());q.add(Choice(choice_text='single option', votes=0));q.save()

what I am trying to do is filter questions by question_text length being more than amount of choices(children):

#from django.db.models import Count,F, Func,Value
#q=Question.objects.all()
#q.annotate(no=Count('choice')).filter(question_text__regex=r'.{3}')#works
#q.annotate(no=Count('choice')).filter(question_text__regex=r'.{'+str(3)+'}')#works
#q.annotate(no=Count('choice')).filter(question_text__regex=r'.{'+str(F('no'))+'}')
#q.annotate(no=Count('choice')).filter(question_text__regex=r'.{'+str(F('nod'))+'}')
#q.filter(question_text__regex=r'.{'+str(F('choice__count'))+'}')   
#q.filter(question_text__regex=r'.{'+str(Count('choice'))+'}')
#Question.objects.filter(question_text__regex = r'.{'+(str(Count('choice')))+'}')
#q.filter(question_text__regex=r'.{'+str(Count([1]))+'}')
#q.filter(question_text__regex=r'.{'+str(Count([1,2,2,2,2,2,2,2,2,2,2,2,2,2]))+'}')
#q.annotate(no=Func(F('question_text'), function='LENGTH')).filter(question_text__regex=r'.{'+str(F("no"))+'}')
#q.annotate(no=Func(F('question_text'), function='LENGTH')).filter(no__gte=F('choice__count'))#works
#q.filter(question_text__regex=r'.{'+str(F("choice__count"))+'}')
#q.filter(question_text__regex=r'.{'+str(("choice__count"))+'}')
#q.filter(question_text__regex=r'.{'+str(Count("choice__count"))+'}')
#q.filter(question_text__regex=r'.{'+str(Count("choice"))+'}')
#q.filter(question_text__regex=r'.{'+str(Value("choice__count"))+'}')
#q.filter(question_text__regex=r'.{'+str(Value("choice__count"))+'}')

question, which has length longer than amount of choices