@Override
        public boolean test(final Traverser<A> traverser) {
            return !traverser.get().key().equals(partitionKey);
        }
A concrete lambda implementation that filters out the partition key so that it isn't visible when making
calls to {@link GraphTraversal#valueMap}.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/decoration/PartitionStrategy.java