matchedWords
Aggregator<InputT,OutputT> matchedWords
Concept #3: A custom aggregator can track values in your pipeline as it runs. Those
values will be displayed in the Dataflow Monitoring UI when this pipeline is run using the
Dataflow service. These aggregators below track the number of matched and unmatched words.
Learn more at https://cloud.google.com/dataflow/pipelines/dataflow-monitoring-intf about
the Dataflow Monitoring UI.