Blend into extant scene

[gerritholl]

When using MultiScene.blend, allow the user to bring their own scene into which the new datasets will be written. With the added flexibility this allows, the user may be able to load from a blended scene.

• Closes Load from blended scene #1749 with workaround
• Tests added
• Fully documented

[gerritholl]

If #1751 is merged first, I can commit the documentation of the new feature here after.

[codecov]

Codecov Report

Merging #1752 (e7ff2ea) into main (142922d) will increase coverage by 0.17%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1752      +/-   ##
==========================================
+ Coverage   93.01%   93.19%   +0.17%     
==========================================
  Files         271      271              
  Lines       39579    40372     +793     
==========================================
+ Hits        36816    37623     +807     
+ Misses       2763     2749      -14     

Flag	Coverage Δ
behaviourtests	4.64% <6.66%> (+0.18%)	⬆️
unittests	93.76% <100.00%> (+0.15%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
satpy/multiscene.py	92.98% <100.00%> (+2.10%)	⬆️
satpy/tests/test_multiscene.py	99.48% <100.00%> (+0.02%)	⬆️
satpy/composites/config_loader.py	85.49% <0.00%> (-0.61%)	⬇️
satpy/readers/caliop_l2_cloud.py	11.47% <0.00%> (-0.60%)	⬇️
satpy/readers/li_l2.py	13.33% <0.00%> (-0.46%)	⬇️
satpy/readers/ghrsst_l3c_sst.py	7.24% <0.00%> (-0.22%)	⬇️
satpy/composites/glm.py	100.00% <0.00%> (ø)
satpy/readers/omps_edr.py	100.00% <0.00%> (ø)
satpy/tests/test_utils.py	100.00% <0.00%> (ø)
satpy/tests/test_dataset.py	100.00% <0.00%> (ø)
... and 161 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 142922d...e7ff2ea. Read the comment docs.

[coveralls]

Coverage increased (+0.01%) to 93.695% when pulling e7ff2ea on gerritholl:blend-into-extant-scene into 142922d on pytroll:main.

[djhoese]

Is this a workaround for the #1747? Is it needed otherwise? I'd prefer not to merge this if not. If something like this is needed I think I'd prefer something like a Scene.update method to combine to Scenes together.

[gerritholl]

Is this a workaround for the #1747?

Partly. More directly, it's a workaround for #1749. I suppose that if #1747 was fixed properly, then #1749 would be closed as well.

Is it needed otherwise?

I don't know.

I'd prefer not to merge this if not. If something like this is needed I think I'd prefer something like a Scene.update method to combine to Scenes together.

How would that work? The object I get back from MultiScene.blend doesn't have any file handlers associated. Could you sketch how I could load from a blended scene with a Scene.update?

[gerritholl]

When finished, #1797 should make the functionality for this PR redundant.