Q:

How to annotate field without duplicate fields django

So I basically have this simple model:
class BaseLesson(models. Model):
    YOUTUBE_VIDEO = '0'
    MARKDOWN = '1'

    TYPE_CHOICES = (
        (YOUTUBE_VIDEO, 'youtube-video'),
        (MARKDOWN, 'markdown'),
    )

    type = models. CharField(
        max_length=10, choices=TYPE_CHOICES, default=MARKDOWN, verbose_name=_('type'))

    shown_users = models. ManyToManyField(
        User, related_name='lessons', verbose_name=_('shown users'), blank=True)

    objects = managers. BaseLessonManager()

There is a many-to-many relationship with the User model in shown_users
And I wanna annotate the is_shown status based on the many-to-many table, so I did this:
class BaseLessonManager(InheritanceManager, CachingManager):
    def get_lesson_with_is_shown(self, user):

        shown_user_case = django_models. Case(
            django_models. When(shown_users__id=user.id,
                               then=django_models. Value(True)),
            default=django_models. Value(False),
            output_field=django_models. BooleanField())

        return self.get_queryset().annotate(
            is_shown=shown_user_case)

The problem with this is that if user1 and user2 saw the same lesson it will be duplicate, for example:
+-----------------+-----------+
|    lesson_id    |  user_id  |
+-----------------+-----------+
|        1        |     1     |
|        1        |     2     |
|        1        |     3     |
+-----------------+-----------+

For such case, I will get these duplicated lessons:
            {
                "id": 1
                "type": "0",
                "is_shown": true
            },
            {
                "id": 1
                "type": "0",
                "is_shown": false
            },
            {
                "id": 1
                "type": "0",
                "is_shown": false
            }

So it's checking each related lesson field in the SHOWN_USERS table... sample photo:
https://imgur.com/GJCPWjk
What I tried so far:
1.  Exclude:
I added an exclude expression to get rid of the extra lessons:
return self.get_queryset().annotate(
       is_shown=shown_user_case).exclude(
       django_models. Q(is_shown=False) & django_models. Q(shown_users__id=user.id))

And I think this is super ugly cuz if I have 1000 users and 50 lessons it means I'm taking all 50000 fields then filter 50 of them :(
Is there any cleaner way to do that ? 
2.  Distinct:
I have tried distinct before and it's not fixing the problem, instead of shown the lesson three times it will show:

once (is_shown = True), 
and another time (is_shown = False)

Here is the github repo if you wanna experiment:
https://github.com/coretabs-academy/website-v2

A:

I managed to fix the problem, and If figured out that my way of querying many-to-many is the problem, instead of shown_users__id == user.id I used id__in==user.lessons.values('id'), full code:
class BaseLessonManager(InheritanceManager, CachingManager):
    def with_is_shown(self, user):

        user_shown_lessons = user.lessons.values('id')

        shown_user_case = django_models. Case(
            django_models. When(id__in=user_shown_lessons,
                           then=django_models. Value(True)),
            default=django_models. Value(False),
            output_field=django_models. BooleanField())

        return self.get_queryset().annotate(
            is_shown=shown_user_case)

