@Override
    public LabelledDocument nextDocument() {
        LabelledDocument document = currentIterator.next();
        for (String label : document.getLabels()) {
            labels.storeLabel(label);
        }

        return document;
    }
@ Override public LabelledDocument nextDocument ( ) { LabelledDocument document = currentIterator . next ( ) ; for ( String label : document . getLabels ( ) ) { labels . storeLabel ( label ) ; } return document ; }
This method returns next LabelledDocument from underlying iterator
@return