code: public String[] lemmatize(final String[] tokens) {
      final Span[] origSpans = this.sequenceLabeler.tag(tokens);
      final Span[] seqSpans = SequenceLabelerME.dropOverlappingSpans(origSpans);
      // TODO work with Spans only
      final String[] decodedLemmas = StringUtils.decodeLemmas(tokens, seqSpans);
      return decodedLemmas;
    }
docs: Lemmatize the current sentence.
  
  @param tokens
  the current sentence
  @return the array of span sequences