result_set: {
    stat1: [
            {
                begin: begin_date1,
                end: end_date1,
                stats: [
                    {stat1_val1:count111},
                    {stat1_val2:count112},
                    {stat1_val3:count113},
                ]

            },
            {
                begin: begin_date2,
                end: end_date2,
                stats: [
                    {stat1_val1:count121},
                    {stat1_val2:count122},
                    {stat1_val3:count123},
                ]

            }
        ],
    stat2: [
            {
                begin: begin_date1,
                end: end_date1,
                stats: [
                    {stat2_val1:count211},
                    {stat2_val2:count212},
                    {stat2_val3:count213},
                ]

            },
            {
                begin: begin_date2,
                end: end_date2,
                stats: [
                    {stat1_val1:count221},
                    {stat1_val2:count222},
                    {stat1_val3:count223},
                ]

            }
        ]

}