public List<VertexProperty<?>> getProperty(final TinkerVertex vertex, final String key) {
        // if the vertex property is already on the vertex, use that.
        final List<VertexProperty<?>> vertexProperty = this.getValue(vertex, key);
        return vertexProperty.isEmpty() ? (List) getPropertiesMap(vertex).getOrDefault(key, Collections.emptyList()) : vertexProperty;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/process/computer/TinkerGraphComputerView.java