SQL to ecto: custom order by getting (Postgrex.Error) ERROR 42601 (syntax_error) syntax error at or near "AS"

What am I missing?
I am trying to ‘translate’ following SQL query to ecto:

SELECT g.groupname, g.id FROM groups AS g
LEFT OUTER JOIN unnest ('{class3, class1, class11, latecomer}'::text[]) WITH ORDINALITY sort(sort_order, ord)
ON g.groupname = sort_order
ORDER BY ord

Result:

2024-07-09 17_54_15-DBeaver 24.0.2 - _p1_ Script-4510×185 9.67 KB

My try using ecto:

from g in Backend.Schema.Group,
  left_join:
    sort in fragment(
      "unnest ('{kindergarden, class1, class2, class3, class4}'::text[]) WITH ORDINALITY sort(name, ord)"
    ),
  on: g.groupname == sort.name,
  order_by: sort.ord,
  select: {g.groupname, g.id}

Gives the following:

** (Postgrex.Error) ERROR 42601 (syntax_error) syntax error at or near "AS"

    query: SELECT g0."groupname", g0."id" FROM "groups" AS g0
 LEFT OUTER JOIN unnest ('{kindergarden, class1, class2, class3, class4}'::text[]) WITH ORDINALITY sort(name, ord) AS f1
 ON g0."groupname" = f1."name" ORDER BY f1."ord"

I tried to use as: :sort but this generates the same query…