Fix or add missing specification for code blocks in documentation

[nelsonaloysio]

Simply makes some adjustments to the docstrings to (1) add missing syntax highlighting and (2) fix spacing issues.

For example, the code block in the documentation of transforms.NodePropertySplit is currently not rendered as code.

edit: closed and reopened this from another branch in the fork instead of master, so to open another (unrelated) PR.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.99%. Comparing base (61c47ee) to head (a16f293). Report is 4 commits behind head on master.

:exclamation: Current head a16f293 differs from pull request most recent head cfde1ba

Please upload reports for the commit cfde1ba to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #9326 +/- ## ========================================== + Coverage 87.33% 87.99% +0.66% ========================================== Files 460 471 +11 Lines 30385 30721 +336 ========================================== + Hits 26536 27034 +498 + Misses 3849 3687 -162 ```

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