How to check the existence of an M2M relation??

Question

Django

models:

class User(models.Model):
    ...
    group = models.ManyToManyField(
        Group, related_name="users_group", verbose_name="The User Group"
    )

class Group(models.Model):
    ....

How to check if the group is empty in the serializer (that is, there are no links to User)

My version :

class GroupSerializer(serializers.ModelSerializer):
    
    empty = serializers.SerializerMethodField()
    class Meta:
        ...
        
    def get_empty(self, obj):
        return not User.objects.filter(group=obj).exists()

But maybe there is an even better way.