Function raw_buffer_to_cells 

pub fn raw_buffer_to_cells(
    buf: &[u8],
) -> Result<Vec<(u32, Vec<(u32, CellValue)>)>>

Decode a raw buffer into cell values for applying to a worksheet.

Returns rows as (row_number, cells) where each cell is (col_number, CellValue). Both row and column numbers are 1-based.