public static UnsupportedOperationException identicalMultiPropertiesNotSupported() {
            return new UnsupportedOperationException("Multiple properties on a vertex is supported, but a single key may not hold the same value more than once");
        }
Common exceptions to use with a property.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/VertexProperty.java