Fix docstrings for blackdoc v0.3 by adding newline after block

[weiji14]

Description of proposed changes

Blackdoc v0.3 was released (https://github.com/keewis/blackdoc/releases/tag/v0.3) and this broke our style checks 😅 This is just a quickfix to add some newlines with ... following the change at keewis/blackdoc#62

        ...     )
+       ...

Fixes #

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Notes

• You can write /format in the first line of a comment to lint the code automatically