Junshi Guo

@spmallette Sorry for the late reply. The PR is updated with documentation, python support and tests as requested. `product` and `variance` steps implementation should be very similar. I will implement...

@spmallette Sorry I missed the messages. I am not very familiar with the GLV tests and having trouble fixing the test failures. It seems like the generated `gremlin-javascript/src/main/javascript/gremlin-javascript/test/cucumber/gremlin.js` is not...