Django generic ListView, ссылающийся на каждый элемент в списке object_list

Я хочу узнать количество слушателей для каждого тренинга в ListView, добавляя контекст.

Я искал, как сослаться на каждый элемент в ListView, чтобы выполнить дальнейший запрос к каждому из них.

Если кто-то знает более эффективный способ, я буду благодарен

class TrainingsView(ListView):
    model = NewHireTraining
    template_name = 'nht/trainings.html'
    context_object_name = 'trainings'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['headcount'] = Trainee.objects.filter(new_hire_training = self.SOMETHING).count()
        return context

Добавление моделей NewHireTraining и Trainee:

class NewHireTraining(models.Model):
    location = models.ForeignKey(Location, on_delete=models.CASCADE)
    program = models.ForeignKey(Program, on_delete=models.CASCADE)
    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    trainer = models.ForeignKey(Trainer, on_delete=models.RESTRICT)
    start_date = models.DateField()
    nesting_date = models.DateField()
    production_date = models.DateField()

    def __str__(self):
        return str(self.program) + ' ' + str(self.project) + ' ' + str(self.start_date)


class Trainee(models.Model):
    first_name = models.CharField(max_length=55)
    last_name = models.CharField(max_length=55)
    employee_number = models.IntegerField()
    hire_date = models.DateField()
    is_term = models.BooleanField(default=False)
    new_hire_training = models.ForeignKey(NewHireTraining, on_delete=models.CASCADE, default="")

    def __str__(self):
        return self.first_name + ' ' + self.last_name

from django.db.models import Count

class TrainingsView(ListView):
    model = NewHireTraining
    template_name = 'nht/trainings.html'
    context_object_name = 'trainings'
    queryset = NewHireTraining.objects.annotate(headcount=Count('trainee'))

{% for training in trainings %}
    {{ trailing }}: {{ trailing.headcount }}
{% endfor %}