code: private void populateCurrentKeyValue() throws IOException, InterruptedException {
      currentKey = delegateReader.getCurrentKey();
      currentValue = delegateReader.getCurrentValue();
      ++recordsRead;
    }
docs: Helper for populating currentKey and currentValue from delegateReader. Should only be called
  once per new key/value from the delegateReader; this method is also responsible for tracking
  the number of records read so far.