`WP_List_Table` is essentially an `abstract` class. Some of its methods throw `die()` warnings if they aren't overridden in a child class.
These noop methods wouldn't be `abstract`, because they are not required in subclasses. However, `WP_List_Table` can call these methods in its own method, `->single_row_columns()`, whether a subclass defined them or not.
See #30799.
git-svn-id: https://develop.svn.wordpress.org/trunk@31210 602fd350-edb4-49c9-b593-d223f7449a82