code: public WritableDataPoints newBatch(String metric, Map<String, String> tags) {
      return new BatchedDataPoints(this, metric, tags);
    }
docs: Returns a new {@link BatchedDataPoints} instance suitable for this TSDB.
  
  @param metric Every data point that gets appended must be associated to this metric.
  @param tags The associated tags for all data points being added.
  @return data structure which can have data points appended.