ManyToManyField issue https://groups.google.com/g/django-users/c/8xqiSDok2JA/m/qnn99QalBgAJ

models.py

from django.db import models
from django.db.models.signals import post_save, post_delete
from django.dispatch import receiver


class Contact(models.Model):
    last_name = models.TextField(default='', blank=True)
    connections = models.ManyToManyField('self',
                                         through='ContactConnection',
                                         symmetrical=True,
                                         blank=True)

    def __str__(self):
        return self.last_name

    def get_connections(self):
        return ', '.join([str(p.last_name) for p in self.connections.all()])


class ContactConnection(models.Model):
    to_contact = models.ForeignKey(Contact, on_delete=models.CASCADE, related_name='to_contacts')
    from_contact = models.ForeignKey(Contact, on_delete=models.CASCADE, related_name='from_contacts')
    comments = models.TextField(default='', blank=True)


@receiver(post_save, sender=ContactConnection)
def post_save(sender, instance, created, **kwargs):
    if created:
        sender.objects.get_or_create(to_contact=instance.from_contact,
                                     from_contact=instance.to_contact,
                                     defaults={'comments': instance.comments})

@receiver(post_delete, sender=ContactConnection)
def post_delete(sender, instance, **kwargs):
    sender.objects.filter(to_contact=instance.from_contact,
                          from_contact=instance.to_contact).delete()