om Hu-Bei and not from Hu-Bei; 
            data_hubei = data.filter(datum => {return datum[keyHint] === alone});
            data = data.filter(datum => {return datum[keyHint] !== alone});

            // stack data; 
            let prestack = seqgen(data);
            let prestack_hubei = seqgen(data_hubei);
            // let keys = Array.from(new Set(data.map( datum => datum[keyHint])));
            // sort according to '累计确诊' and prepare keys; 
            const sortedforkey = sequential[seque