@Override
        public void fireEvent(final Iterator<MutationListener> eventListeners) {
            while (eventListeners.hasNext()) {
                eventListeners.next().vertexRemoved(vertex);
            }
        }
Represents an action where a {@link Vertex} is removed from the {@link Graph}.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/event/Event.java