public override void Add(Component c)
 {
     Console.WriteLine("Can not add to a leaf");
 }
 public override void Remove(Component c)
 {
     _children.Remove(c);
 }
 public override void Add(Component c)
 {
     _children.Add(c);
 }
 public abstract void Remove(Component c);
 public abstract void Add(Component c);
 public override void Remove(Component c)
 {
     Console.WriteLine("Can not Remove from a leaf");
 }