/// <summary>
        /// Adds the equivalent label.
        /// </summary>
        /// <returns></returns>
        public EquivalentLabel AddEquivalentLabel()
        {
            var label = new EquivalentLabel();

            Add(label);

            return(label);
        }
 /// <summary>
 /// Adds the item.
 /// </summary>
 /// <param name="label">The label.</param>
 public void AddItem(EquivalentLabel label)
 {
     Add(label);
 }