@Override
    public Set<String> keys() {
        return this.previousMap.keySet().stream().filter(key -> !this.inExecute || this.memoryKeys.get(key).isBroadcast()).collect(Collectors.toSet());
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/process/computer/TinkerMemory.java