Target.description defaults to "" (empty str)
Substrate.thickness defaults to "" (empty str)
Substrate.thickness_unit is now hardcoded to "μm"
did you know? apparently h5py does NOT like null values
get_instruments returns a dictionary with the names of every system used
during the deposition
unfortunately, NeXus standard allows for a single value of all three
keys per every sample - not every layer
this means that every layer has its own data for laser, rheed system and
depo chamber which IDEALLY is the same for every layer, but in practice
they COULD be different and I still don't know how to deal with this
