Improve implementation of characteristics from ACA xija model

[taldcroft]

Description

This improves the implementation of proseco.characteristics (commonly ACA in the code) so that the characteristics that are derived from the chandra_models aca_spec.json thermal model spec always reflect the correct values. This applies even when environment variables like CHANDRA_MODELS_REPO_DIR are changed during program execution.

Previously the values were cached based on the selected repo and version at the first time the characteristics were accessed. The test which changed illustrates how things work more nicely now, in particular no need for explicitly dealing with caching.

Thanks to @jeanconn in #385 (review) for pointing out this possibility.

Interface impacts

None.

Testing

Unit tests

• Mac

Independent check of unit tests by Jean

• Linux

Functional tests

No functional testing.

[jeanconn]

I think this is great!

[jeanconn]

But I ran into an issue from the last PR #385 that I'm surprised passes tests:

(ska3) spark:proseco jean$ ipython
Python 3.10.8 | packaged by conda-forge | (main, Nov 22 2022, 08:27:35) [Clang 14.0.6 ]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.8.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import proseco.tests.test_catalog
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[1], line 1
----> 1 import proseco.tests.test_catalog

File ~/git/proseco/proseco/tests/test_catalog.py:21
     18 from .test_common import DARK40, OBS_INFO, STD_INFO, mod_std_info
     20 # Ensure all plotting is to a non-interactive backend
---> 21 matplotlib.pyplot.switch_backend("agg")
     23 HAS_SC_ARCHIVE = Path(mica.starcheck.starcheck.FILES["data_root"]).exists()
     24 TEST_COLS = "slot idx id type sz yang zang dim res halfw".split()

File ~/miniconda3/envs/ska3/lib/python3.10/site-packages/matplotlib/_api/__init__.py:224, in caching_module_getattr.<locals>.__getattr__(name)
    222 if name in props:
    223     return props[name].__get__(instance)
--> 224 raise AttributeError(
    225     f"module {cls.__module__!r} has no attribute {name!r}")

AttributeError: module 'matplotlib' has no attribute 'pyplot'

[jeanconn]

Granted, I guess it doesn't really matter because the tests aren't meant to be run that way anyway... they need their pytest magics.

[taldcroft]

I wasn't sure if that "auto-import" of pyplot would work when I first wrote the code, but I thought that getting through pytest was a sufficient demonstration. Huh, magics indeed. Anyway, fixed.