public void addVertexProgramMemoryComputeKeys(final VertexProgram<?> vertexProgram) {
        vertexProgram.getMemoryComputeKeys().forEach(key -> this.memoryComputeKeys.put(key.getKey(), key));
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/util/MapMemory.java