fix: python3.9 support

[dolfim-ibm]

Add support for python3.9.

Issue resolved by this Pull Request:
Resolves #385

Checklist:

• Documentation has been updated, if necessary.
• Examples have been added, if necessary.
• Tests have been added, if necessary.

[mergify]

Merge Protections

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🟢 🛡 GitHub branch protections and repository rulesets requirements

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• #approved-reviews-by >= 1 [🛡 GitHub repository ruleset rule main]
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• any of: [🛡 GitHub repository ruleset rule main]
  • check-success = code-checks / run-checks (3.10)
  • check-neutral = code-checks / run-checks (3.10)
  • check-skipped = code-checks / run-checks (3.10)
• any of: [🛡 GitHub repository ruleset rule main]
  • check-success = code-checks / run-checks (3.11)
  • check-neutral = code-checks / run-checks (3.11)
  • check-skipped = code-checks / run-checks (3.11)
• any of: [🛡 GitHub repository ruleset rule main]
  • check-success = code-checks / run-checks (3.12)
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• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?:

[PeterStaar-IBM]

go!