Code formatting with new 'black'

[soininen]

Re spine-tools/Spine-Toolbox#2115

Checklist before merging

• [x] Documentation (also in Toolbox repo) is up-to-date
• [x] Release notes in Toolbox repo have been updated
• [x] Unit tests have been added/updated accordingly
• [x] Code has been formatted by black
• [x] Unit tests pass

[codecov-commenter]

Codecov Report

Patch coverage: 50.00% and no project coverage change.

Comparison is base (3b6c10f) 75.46% compared to head (2e07597) 75.46%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #245 +/- ## ======================================= Coverage 75.46% 75.46% ======================================= Files 76 76 Lines 10895 10895 Branches 2369 2369 ======================================= Hits 8222 8222 Misses 2234 2234 Partials 439 439 ``` | [Impacted Files](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools) | Coverage Δ | | |---|---|---| | [spinedb\_api/export\_mapping/export\_mapping.py](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVkYl9hcGkvZXhwb3J0X21hcHBpbmcvZXhwb3J0X21hcHBpbmcucHk=) | `88.26% <ø> (ø)` | | | [spinedb\_api/graph\_layout\_generator.py](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVkYl9hcGkvZ3JhcGhfbGF5b3V0X2dlbmVyYXRvci5weQ==) | `0.00% <0.00%> (ø)` | | | [spinedb\_api/spine\_io/gdx\_utils.py](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVkYl9hcGkvc3BpbmVfaW8vZ2R4X3V0aWxzLnB5) | `61.53% <0.00%> (ø)` | | | [...inedb\_api/spine\_io/importers/datapackage\_reader.py](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVkYl9hcGkvc3BpbmVfaW8vaW1wb3J0ZXJzL2RhdGFwYWNrYWdlX3JlYWRlci5weQ==) | `62.96% <ø> (ø)` | | | [.../versions/1e4997105288\_separate\_type\_from\_value.py](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVkYl9hcGkvYWxlbWJpYy92ZXJzaW9ucy8xZTQ5OTcxMDUyODhfc2VwYXJhdGVfdHlwZV9mcm9tX3ZhbHVlLnB5) | `94.54% <100.00%> (ø)` | | | [spinedb\_api/helpers.py](https://app.codecov.io/gh/spine-tools/Spine-Database-API/pull/245?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVkYl9hcGkvaGVscGVycy5weQ==) | `57.93% <100.00%> (ø)` | |

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