/// <summary>
 /// Adds the specified callback.
 /// </summary>
 /// <typeparam name="TEvent">The type of the event.</typeparam>
 /// <param name="callback">The callback.</param>
 public void Add <TEvent>(Action <TEvent> callback)
 {
     CallbacksInternal.Add(callback);
 }
 /// <summary>
 /// Removes the specified callback.
 /// </summary>
 /// <typeparam name="TEvent">The type of the event.</typeparam>
 /// <param name="callback">The callback.</param>
 public void Remove <TEvent>(Action <TEvent> callback)
 {
     CallbacksInternal.Remove(callback);
 }
 /// <summary>
 /// Clear all callbacks from this store.
 /// </summary>
 public void Clear()
 {
     CallbacksInternal.Clear();
 }