checking custom connections according to PEP 249

[mehtamohit013]

Describe your changes

Added PEP 249 compliance to custom connection.
Checking whether the connection object has close, commit and rollback methods

Issue number

Closes #433

Checklist before requesting a review

• Performed a self-review of my code
• Formatted my code with pkgmt format
• Added tests (when necessary).
• Added docstring documentation and update the changelog (when needed)

---

📚 Documentation preview 📚: https://jupysql--517.org.readthedocs.build/en/517/

[edublancas]

can you add some tests?

also, please check that the problem I reported is also fixed

[mehtamohit013]

@edublancas
Yup, it is working as expected

Code cell:

%load_ext sql
%sql duckdb://
df = 1
%sql --persist df

[tonykploomber]

Minor

ready to merge