Function: Utility function to traverse the multidimensional array and apply user function.

Function: Saves the course, lesson, topic, and quiz settings meta to separate post meta.

Function: Prints the given string in preformated text.

Function: Redirects to the home page if the user lands on archive pages for lesson or quiz post types.

Function: Checks Whether the learndash license is valid or not.

Function: Loads editor styles for LearnDash.

Function: Loads the certificate image as the background for the visual editor.