Permit empty graphs

[liamhuber]

I.e.

import pyiron_workflow as pwf

wf = pwf.Workflow("empty")
wf()
>>> {}

Closes pyiron/pyironFlow#48

[github-actions]

👈 Launch a binder notebook on branch pyiron/pyiron_workflow/permit_empty_graphs

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.00% (target: -1.00%)	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (7c66e2d)	3432	3136	91.38%
Head commit (4852ecf)	3433 (+1)	3137 (+1)	91.38% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#606)	3	3	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[coveralls]

Pull Request Test Coverage Report for Build 13549615693

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.003%) to 91.378%

---

Files with Coverage Reduction	New Missed Lines	%
nodes/composite.py	3	92.24%

Totals
Change from base Build 13540837226:	0.003%
Covered Lines:	3137
Relevant Lines:	3433

---

💛 - Coveralls