code: public static boolean isStartOfChunk(LabelTagType prev, LabelTagType cur)
    {
      if (prev == null) {
        return isStartOfChunk("O", "O", cur.tag, cur.type);
      } else {
        return isStartOfChunk(prev.tag, prev.type, cur.tag, cur.type);
      }
    }
docs: Returns whether a chunk started between the previous and current token
  @param prev - the label/tag/type of the previous token
  @param cur - the label/tag/type of the current token
  @return true if the current token was the first token of a chunk