public sealed class Developers : List<Developer> {
  public Developers(IEnumerable<Developer> items) : base(items) { }
}

public static class DevelopersExtension {
  public static IEnumerable<Developer> Where(
    this Developers source, Func<Developer, bool> predicate) {

    Console.WriteLine("Dolo k voln roziujc metody Where pro objekt typu Developers");
    return (source.AsEnumerable().Where(predicate));
  }

  public static IEnumerable<Developer> Where(
    this Developers source,
    Func<Developer, int, bool> predicate) {

    Console.WriteLine("Dolo k voln roziujc metody pro objekt typu Developers");
    return (source.AsEnumerable().Where(predicate));
  }
}
