docs: public static void main(String[] args) throws Exception {
  		ExecutionEnvironment env = ExecutionEnvironment.createCollectionsEnvironment();
  		BatchTableEnvironment tEnv = BatchTableEnvironment.create(env);
  
  		DataSet<WC> input = env.fromElements(
  				new WC("Hello", 1),
  				new WC("Ciao", 1),
  				new WC("Hello", 1));
  
  		Table table = tEnv.fromDataSet(input);
  
  		Table filtered = table
  				.groupBy("word")
  				.select("word, frequency.sum as frequency")
  				.filter("frequency = 2");
  
  		DataSet<WC> result = tEnv.toDataSet(filtered, WC.class);
  
  		result.print();
  	}