Use h5py as an independent check.

[1uc]

Write-read cycles have the flaw that they can't detect certain bugs, e.g. if the array is column-major instead of row-major a simply write-read cycles using always the same types, wont fail.

One idea is to use h5py to act as an independent check. We would write in HighFive/h5py then read in h5py/HighFive.