Return the list of pretty app names that are available in the database.

        Returns:
            set of str.

def get_pretty_app_names(self):
        """
        Return the list of pretty app names that are available in the database.

        Returns:
            set of str.
        """
        pretty_app_names = set()
        for app_name in self.get_app_names():
            pretty_app_names.add(self.get_name(app_name))

        return pretty_app_names