// 1. atomically swap the listeners with TOMBSTONE, this is because addListener uses that
    //    to synchronize with us
    // 2. reverse the linked list, because despite our rather clear contract, people depend on us
    //    executing listeners in the order they were added
    // 3. push all the items onto 'onto' and return the new head of the stack
    Listener head = ATOMIC_HELPER.gasListeners(this, Listener.TOMBSTONE);

  }

  /**
   * Returns a view of a multimap whose values are derived from the original multimap's entries. In
   * contrast to {@link #transformValues}, this method's entry-transformation logic may depend on
   * the key as well as the value.
   *
   * <p>All other properties of the transformed multimap, such as iteration order, are left intact.
   * For example, the code:
   *
   * <pre>{@code