code: private String print(final List<Span> spans, final String[] toks) {
      return Arrays.toString(
          Span.spansToStrings(spans.toArray(new Span[spans.size()]), toks));
    }
docs: Auxiliary method to print spans
  
  @param spans
  the span list
  @param toks
  the tokens array
  @return the spans as string