Part connector (Sourcery refactored)

[sourcery-ai]

Pull Request #363 refactored by Sourcery.

If you're happy with these changes, merge this Pull Request using the Squash and merge strategy.

NOTE: As code is pushed to the original Pull Request, Sourcery will
re-run and update (force-push) this Pull Request with new refactorings as
necessary. If Sourcery finds no refactorings at any point, this Pull Request
will be closed automatically.

See our documentation here.

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Review changes via command line

To manually merge these changes, make sure you're on the part-connector branch, then run:

git fetch origin sourcery/part-connector
git merge --ff-only FETCH_HEAD
git reset HEAD^

[sourcery-ai]

Sourcery Code Quality Report (beta)

✅  Merging this PR will increase code quality in the affected files by 0.04 out of 10.

Quality metrics	Before	After	Change
Complexity	1.29	1.00	-0.29 🔵
Method Length	33.42	33.28	-0.14 🔵
Quality	9.05	9.09	0.04 🔵

Other metrics	Before	After	Change
Lines	66	64	-2

Changed files	Quality Before	Quality After	Quality Change
gaphor/SysML/blocks/connectors.py	9.05	9.09	0.04 🔵

Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

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