check class exists for smart lists (and others)

Hi folks,

Could I make a feature request for future revisions that you wrap your class definitions for smart lists in particular with “class_exists” checks ?

I had need to make some adjustment to one of the smart list formats and its not trivial to override with a child class because the class files are loaded with require_once.

If they are wrapped to check if the class is already defined then I could simply include my versions in the child theme from functions.php without causing a PHP runtime error.

Would be super helpful, thanks !