public default <V> void forEach(final BiConsumer<String, V> biConsumer) {
        this.keys().forEach(key -> biConsumer.accept(key, this.<V>get(key)));
    }
If sacks are enabled and a merge function has been specified, then get it (else get <code>null</code>).
The merge function is used to merge two sacks when two {@link Traverser}s converge.

@param <S> the sack type
@return the operator for merging two traverser sacks
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/TraversalSideEffects.java