The body: IWorksheet.JSON for a worksheet, IOpaqueSheet.JSON for the other kinds.
OptionalkindWhat the sheet holds, and so what sheet is.
A unique name for the sheet.
OptionalsheetThe sheet's body.
OptionalsheetThe origin format's own identifier for this sheet, preserved so a round trip does not renumber it.
Interop only — nothing in the model reads it and nothing references it by value. It is
arbitrary and sparse (a workbook's edit history leaves gaps, so Jan=3, Feb=28, Mar=29 is
ordinary) and is not the sheet's position: localSheetId on a defined name is a
position and is resolved separately. Absent for a sheet that was never loaded from a file;
a writer assigns one in that case.
Optionalvisibility
Used for persisting an ISheet: its tab, and its body as SheetRefJSON.kind says.