private Map<String, List<VertexProperty>> getPropertiesMap(final TinkerVertex vertex) {
        Map<String, List<VertexProperty>> propertiesMap = TinkerHelper.getProperties(vertex);
        if (retainVertexProperties != null) {
            propertiesMap.keySet().retainAll(retainVertexProperties);
        }
        return propertiesMap;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/process/computer/TinkerGraphComputerView.java