[patch] Use consistent and canonical cls/self for (non)classmethod

[liamhuber]

Just correcting some silly little accidents that slipped into the tests.

[github-actions[bot]]

:point_left: Launch a binder notebook on branch _pyiron/pyiron_workflow/classmethodmixup

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
:white_check_mark: +0.00% (target: -1.00%)	:white_check_mark: ∅

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (b1ad266650e2d88dfc1cef7572bcd8975059ae27) | 3303 | 2890 | 87.50% | | | Head commit (c52cd1e8fcceb704031e8125fb77b2d0cbcc9a68) | 3303 (+0) | 2890 (+0) | 87.50% (**+0.00%**) | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#256) | 0 | 0 | **∅ (not applicable)** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

See your quality gate settings    Change summary preferences

_{You may notice some variations in coverage metrics with the latest Coverage engine update. For more details, visit the documentation}