code: @Override
      public boolean addToken(T element) {
          boolean ret = false;
          T oldElement = vocabulary.putIfAbsent(element.getStorageId(), element);
          if (oldElement == null) {
              //putIfAbsent added our element
              if (element.getLabel() != null) {
                  extendedVocabulary.put(element.getLabel(), element);
              }
              oldElement = element;
              ret = true;
          } else {
              oldElement.incrementSequencesCount(element.getSequencesCount());
              oldElement.increaseElementFrequency((int) element.getElementFrequency());
          }
          totalWordCount.addAndGet((long) oldElement.getElementFrequency());
          return ret;
      }
docs: This method adds specified SequenceElement to vocabulary
  
  @param element the word to add