How to annotate to query with a custom function in Django ORM?

Question

I have this model:

class Brand(models.Model):
    name = models.CharField(max_length=32)

and this function that returns a number that shows similarity between two strings (a number between 0 and 1).

from difflib import SequenceMatcher
def similar(a, b):
    return SequenceMatcher(None, a, b).ratio()

I want to annotate a column to my query that shows similarity value between name and a string and order them by similarity.

I wrote something like this but it won't work and I don't know how it works.

Brand.objects.all().annotate(
    similarity=ExpressionWrapper(similar(F('name'), 'mercedes'), 
                                 output_field=models.DecimalField()).order_by('similarity')
)

If there is another way to do it please let me know.