Function ncd_matrix_bytes 

pub fn ncd_matrix_bytes(
    datas: &[Vec<u8>],
    method: &str,
    variant: NcdVariant,
) -> Vec<f64>

Computes an NCD matrix (row-major, len = n*n) for in-memory byte blobs.

Note: For symmetric variants, this computes each unordered pair once and writes both (i,j) and (j,i).