How to add expression between window and alias in WindowStatement ?

[SteelAlloy]

Hi, I would like to translate this SQL expression in sea-query :

LEAD(users.uuid) OVER (
    ORDER BY
      users.family_name ASC, users.uuid ASC
  ) IS NOT NULL AS "has_next_row"

So far I've managed to turn the sql into this :

Query::select()
.expr_window_as(
    Expr::cust("LEAD(users.uuid)"),
    WindowStatement::new().order_by_columns([
        (users::Column::FamilyName, Order::Asc),
        (users::Column::Uuid, Order::Asc),
    ]).take(),
    Alias::new("has_next_row"))

But I can't manage to add IS NOT NULL between the window and the alias

The following does not work :

Query::select()
.expr_window_as(
    Expr::expr(Expr::cust("LEAD(users.uuid)")).is_not_null(),
    WindowStatement::new().order_by_columns([
        (users::Column::FamilyName, Order::Asc),
        (users::Column::Uuid, Order::Asc),
    ]).take(),
    Alias::new("has_next_row"))

as it generates :

  LEAD(users.uuid) IS NOT NULL OVER (
    ORDER BY
      users.family_name ASC, users.uuid ASC
  ) AS "has_next_row",

rather than

  LEAD(users.uuid) OVER (
    ORDER BY
      users.family_name ASC, users.uuid ASC
  ) IS NOT NULL AS "has_next_row",

Thanks