How to work with and load/save sparse compressed matrices? (numir, mir.sparse)

[Shaleen Chhabra via Digitalmars-d-learn]

I wish to use load / save for sparse compressed matrices using 
mir.

    import mir.sparse;
    auto sp = sparse!double(5, 8);
    auto crs = sp.compress;

How can I save/load sparse compressed arrays in `npz` format?
(format: ``csc``, ``csr``, ``bsr``, ``dia`` or coo``)

how can i again decompress the compressed sparse array to dense?

Thanks
Shaleen