@Override
            public void vertexPropertyPropertyRemoved(final VertexProperty element, final Property property) {
                assertEquals(vp, element);
                assertEquals(p, property);
                assertEquals("dah", property.value());
                assertEquals("to-drop", property.key());
                triggered.set(true);
            }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/decoration/EventStrategyProcessTest.java