2 positional argument(s) expected, but 1 found. flutter code example

Example 1: flutter too many positional arguments 0 expected but 1 found

Notification notif =
  Notification(description: u["description"], nom_ligne: u["nom_ligne"], created_at: u["created_at"]);

Example 2: flutter too many positional arguments 0 expected but 1 found

const Notification(this.description, this.nom_ligne, this.created_at);