new_contents: import random
  
  class Collection:
      """ A collection of information to be practiced. """
  
      def __init__(self, name):
          self.name = name
          self.slides = []
  
      def add_slide(self, slide):
          """ Add a slide to the collection. """
          self.slides.append(slide)
  
      def remove_slide(self, slide):
          """ Remove a slide from the collection. """
          self.slides.remove(slide)
  
      def get_random_slides(self, n, rand=random):
          """ Return a list of randomly selected slides.
  
              Variables:
              n       int     Number of slides to return
              rand    object  Source for randomness. Defaults to "random".
          """
  
          return rand.sample(self.slides, n)
  
subject: Add Collection class