code: def get_mentions(status_dict, exclude=[]):
      
      # Canonicalise the exclusion dictionary by lowercasing all names and
      # removing leading @'s
      for i, user in enumerate(exclude):
          user = user.casefold()
          if user[0] == "@":
              user = user[1:]
  
          exclude[i] = user
  
      users = [user["username"] for user in status_dict["mentions"]
               if user["username"].casefold() not in exclude]
      return users
docs: Given a status dictionary, return all people mentioned in the toot,
      excluding those in the list passed in exclude.