Function cells_to_raw_buffer 

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

Encode cell values into a raw buffer for transfer.

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