code: public void typeSystemInit(TypeSystem typeSystem)
        throws AnalysisEngineProcessException {
      
      // sentence type
      mSentenceType = AnnotatorUtil.getRequiredTypeParameter(this.context, typeSystem,
          UimaUtil.SENTENCE_TYPE_PARAMETER);
      
      // token type
      mTokenType = AnnotatorUtil.getRequiredTypeParameter(context, typeSystem,
          UimaUtil.TOKEN_TYPE_PARAMETER);
  
      // pos feature
      mPosFeature = AnnotatorUtil.getRequiredFeatureParameter(context, mTokenType, UimaUtil.POS_FEATURE_PARAMETER, 
      		CAS.TYPE_NAME_STRING);
      
      mLexemeFeature = AnnotatorUtil.getRequiredFeatureParameter(this.context, mTokenType,
          "opennlp.uima.LexemeFeature", CAS.TYPE_NAME_STRING);
      
      // featurizer feature
      mFeaturizerFeature = AnnotatorUtil.getRequiredFeatureParameter(context, mTokenType,
              FEATURIZER_TAG_FEATURE_PARAMETER, CAS.TYPE_NAME_STRING);
    }
docs: Initializes the type system.