code: @Override
      public void process(JCas jCas) throws AnalysisEngineProcessException {
          for (Token t : JCasUtil.select(jCas, Token.class)) {
              String pos = BlueCasUtil.getSinglePosTag(t);
              String lemma = lemmatize(t.getCoveredText(), pos);
              if (lemma != null)
                  t.setLemmaStr(lemma);
          }
      }
docs: This process(JCas) method cycles through all annotations in the CAS. For
  those that are identified as tokens by {@link AnnotationDataExtractor}
  implementation being used, an attempt is made to extract part-of-speech
  information. The covered text for each token is then lemmatized using the
  {@link BioLemmatizer}, using the part-of-speech information if it was
  available.