How to use the genie-toolkit.ContextExtractor function in genie-toolkit

//    would use too much memory
            // 2) We need to do multiple passes over the basic dataset for different reasons, and
            //    we can't cache it in memory
            const { path: basicDataset, fd: basicDatasetFD } =
                await tmp.file({ mode: 0o600, dir: '/var/tmp' });

            await StreamUtils.waitFinish(basicSource
                .pipe(new Genie.DatasetStringifier())
                .pipe(fs.createWriteStream(basicDataset, { fd: basicDatasetFD })));
            // basicDatasetFD is closed here

            let contexts = await
                fs.createReadStream(basicDataset, { encoding: 'utf8' })
                .pipe(byline())
                .pipe(new Genie.DatasetParser({ contextual: false }))
                .pipe(new Genie.ContextExtractor(this._schemas))
                .read();

            const contextualized =
                fs.createReadStream(basicDataset, { encoding: 'utf8' })
                .pipe(byline())
                .pipe(new Genie.DatasetParser({ contextual: false }))
                .pipe(new Genie.Contextualizer(contexts, {
                    locale: this._language,
                    numSamples: 20,
                    nullOnly: false,
                }));

            const contextualSynthetic = genSynthetic.generate(tmpDir, {
                contextual: true,
                contexts,