'Returns PaidCourseRegistration object if user has payed for
the course enrollment else Returns None'

@classmethod
def get_course_item_for_user_enrollment(cls, user, course_id, course_enrollment):

    try:
        return cls.objects.filter(course_id=course_id, user=user, course_enrollment=course_enrollment, status='purchased').latest('id')
    except PaidCourseRegistration.DoesNotExist:
        return None
