Function decode_uncoupled_layer 

pub fn decode_uncoupled_layer(
    params: &DecodeParams,
    erased_chunks: &BTreeSet<usize>,
    z: usize,
    sub_chunk_size: usize,
    u_buf: &mut [Vec<u8>],
) -> Result<(), ClayError>

Decode uncoupled layer using RS MDS code