docs: public static KerasTokenizer fromJson(String jsonFileName) throws IOException, InvalidKerasConfigurationException {
          String json = new String(Files.readAllBytes(Paths.get(jsonFileName)));
          Map<String, Object> tokenizerBaseConfig = parseJsonString(json);
          Map<String, Object> tokenizerConfig;
          if (tokenizerBaseConfig.containsKey("config"))
              tokenizerConfig = (Map<String, Object>) tokenizerBaseConfig.get("config");
          else
              throw new InvalidKerasConfigurationException("No configuration found for Keras tokenizer");
  
  
          Integer numWords = (Integer) tokenizerConfig.get("num_words");
          String filters = (String) tokenizerConfig.get("filters");
          Boolean lower = (Boolean) tokenizerConfig.get("lower");
          String split = (String) tokenizerConfig.get("split");
          Boolean charLevel = (Boolean) tokenizerConfig.get("char_level");
          String oovToken = (String) tokenizerConfig.get("oov_token");
          Integer documentCount = (Integer) tokenizerConfig.get("document_count");
  
          @SuppressWarnings("unchecked")
          Map<String, Integer> wordCounts = (Map) parseJsonString((String) tokenizerConfig.get("word_counts"));
          @SuppressWarnings("unchecked")
          Map<String, Integer> wordDocs = (Map) parseJsonString((String) tokenizerConfig.get("word_docs"));
          @SuppressWarnings("unchecked")
          Map<String, Integer> wordIndex = (Map) parseJsonString((String) tokenizerConfig.get("word_index"));
          @SuppressWarnings("unchecked")
          Map<Integer, String> indexWord = (Map) parseJsonString((String) tokenizerConfig.get("index_word"));
          @SuppressWarnings("unchecked")
          Map<Integer, Integer> indexDocs = (Map) parseJsonString((String) tokenizerConfig.get("index_docs"));
  
          KerasTokenizer tokenizer = new KerasTokenizer(numWords, filters, lower, split, charLevel, oovToken);
          tokenizer.setDocumentCount(documentCount);
          tokenizer.setWordCounts(wordCounts);
          tokenizer.setWordDocs(new HashMap<>(wordDocs));
          tokenizer.setWordIndex(wordIndex);
          tokenizer.setIndexWord(indexWord);
          tokenizer.setIndexDocs(indexDocs);
  
          return tokenizer;
      }