code: void get_cluster_features(final Context ctx,
                                final List<Integer> cluster4,
                                final List<Integer> cluster6,
                                final List<Integer> cluster,
                                List<Integer> features)
      {
          if (!use_cluster)
          {
              return;
          }
  
          PUSH(features, CLUSTER(cluster, ctx.S0));
          PUSH(features, CLUSTER4(cluster4, ctx.S0));
          PUSH(features, CLUSTER6(cluster6, ctx.S0));
          PUSH(features, CLUSTER(cluster, ctx.S1));
          PUSH(features, CLUSTER(cluster, ctx.S2));
          PUSH(features, CLUSTER(cluster, ctx.N0));
          PUSH(features, CLUSTER4(cluster4, ctx.N0));
          PUSH(features, CLUSTER6(cluster6, ctx.N0));
          PUSH(features, CLUSTER(cluster, ctx.N1));
          PUSH(features, CLUSTER(cluster, ctx.N2));
          PUSH(features, CLUSTER(cluster, ctx.S0L));
          PUSH(features, CLUSTER(cluster, ctx.S0R));
          PUSH(features, CLUSTER(cluster, ctx.S0L2));
          PUSH(features, CLUSTER(cluster, ctx.S0R2));
          PUSH(features, CLUSTER(cluster, ctx.S0LL));
          PUSH(features, CLUSTER(cluster, ctx.S0RR));
          PUSH(features, CLUSTER(cluster, ctx.S1L));
          PUSH(features, CLUSTER(cluster, ctx.S1R));
          PUSH(features, CLUSTER(cluster, ctx.S1L2));
          PUSH(features, CLUSTER(cluster, ctx.S1R2));
          PUSH(features, CLUSTER(cluster, ctx.S1LL));
          PUSH(features, CLUSTER(cluster, ctx.S1RR));
      }
docs: 获取词聚类特征
  @param ctx 上下文
  @param cluster4
  @param cluster6
  @param cluster
  @param features 输出特征