fake spectrometer does not properly update mapping id

[ksunden]

yaq-python/yaqd-fakes/yaqd_fakes/_fake_spectrometer.py

Line 28 in c686c34

self._mappings["wavelengths"] = self._gen_mapping()

Since we use set_item here, the mapping id does not get updated by the mix-in class, which requires that you do specifically self._mappings = new_mapping.

I expect this may be a common error, perhaps we should look into solutions to make the version that at least rewrites the top level of entries automatically properly increment mapping_id.

[ksunden]

Additionally, the mapping is not computed until a measurement is taken, so if you ask for mapping first it will be outdated.