Fixed typo with `model.isValid()` in docs.

`model.isValid()` is a function and was missing trailing parenthesis.
Merge pull request #2903 from clayzermk1/master

Fixed typo with `model.isValid()` in docs
Split up long lines for style and readability.
Merge pull request #2905 from braddunbar/line-length

Split up long lines for style and readability.
Tweaking #2905 -- long line styles.