code: public static GISModel trainModel(int iterations, DataIndexer indexer) {
             return trainModel(iterations,indexer,true,false);   
      }
docs: Train a model using the GIS algorithm.
  @param iterations The number of GIS iterations to perform.
  @param indexer The object which will be used for event compilation.
  @return The newly trained model, which can be used immediately or saved
  to disk using an opennlp.maxent.io.GISModelWriter object.