private final void checkKeyValue(final String key, final Object value) {
        if (!this.memoryComputeKeys.containsKey(key))
            throw GraphComputer.Exceptions.providedKeyIsNotAMemoryComputeKey(key);
        MemoryHelper.validateValue(value);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/util/MapMemory.java