In Only Office

I got table where A1 is =SUM(B1,C1)

in OnlyOffice API I trying to paste in A2 value of A1 with relative formula addresses

Expected result A2 is =SUM(B2,C2)

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Actual Resul
A2 is =SUM(B1,C1)

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Source Code

(function()
{
    var sheet = Api.GetActiveSheet();
    var tagetRange = sheet.GetRange("A2");
    var sourceRange = sheet.GetRange("A1");
    tagetRange.Paste(sourceRange)
})();