code: private void printErrors(final List<Span> falsePositives,
        final List<Span> falseNegatives, final String[] toks) {
      this.printStream.println("False positives: {");
      this.printStream.println(print(falsePositives, toks));
      this.printStream.println("} False negatives: {");
      this.printStream.println(print(falseNegatives, toks));
      this.printStream.println("}\n");
    }
docs: Auxiliary method to print span errors
  
  @param falsePositives
  false positives span
  @param falseNegatives
  false negative span
  @param toks
  the document tokens