/// <summary> Notify listeners that the specified edge was removed.
        ///
        /// </summary>
        /// <param name="edge">the edge that was removed.
        /// </param>
        protected internal virtual void  fireEdgeRemoved(Edge edge)
        {
            GraphEdgeChangeEvent e = createGraphEdgeChangeEvent(GraphEdgeChangeEvent.EDGE_REMOVED, edge);

            for (int i = 0; i < m_graphListeners.Count; i++)
            {
                GraphListener l = (GraphListener)m_graphListeners[i];

                l.edgeRemoved(this, e);
            }
        }