public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        String pagerank = "1.0\t";
        boolean first = true;
        for (Text value : values) {
            if(!first) pagerank += ",";
            pagerank += value.toString();
            first = false;
        }
        context.write(key, new Text(pagerank));
    }