docs: @Override
  	public int generateAt(Instance instance, IFeatureAlphabet features, int pos,
  			int... numLabels) {
  		String[][] data = ( String[][]) instance.getData();
  		int len = data[0].length;
  
  		StringBuilder sb = new StringBuilder();
  
  		sb.append(id);
  		sb.append(':');
  		pos = pos+idx;
  		if(pos<0||pos>=len)
  			return -1;
  		char c = data[0][pos].charAt(0); //这里数据行列和模板中行列相反
  		// 得到字符串类型		
  		if(!set.contains(c)){
  			return -1;
  		}
  	int index = features.lookupIndex(sb.toString(),numLabels[0]);
  	return index;
  }