@Override
    public <V> V get(final String key) throws IllegalArgumentException {
        return (null != this.memory && this.memory.exists(key)) ? this.memory.get(key) : this.sideEffects.get(key);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/traversal/MemoryTraversalSideEffects.java