How to access ManyToManyField value from django signal?

Question

I have a following model and function signal_task which just outputs the test_users field objects on signal post_save

class Test_Model(models.Model):
    test_users = models.ManyToManyField(User)

    def signal_task(self):
        print(self.test_users.all())

@receiver(post_save,sender=Test_Model)
def Test_signal(sender,instance=None,created=False,**kwargs):
    if created:
        instance.signal_task()

• On Creating Test_Model objects, singal_task() executes which should output the User objects assigned to test_users, But it outputs the empty queryset <QuerySet []> , How do i output the test_users value?