public static function retrieveByCourseSubjectStudent(CourseSubjectStudent $course_subject_student, $school_year = null)
 {
     $c = new Criteria();
     $c->add(self::CAREER_SUBJECT_ID, $course_subject_student->getCourseSubject()->getCareerSubject()->getId());
     $c->add(self::STUDENT_ID, $course_subject_student->getStudentId());
     if ($school_year) {
         $c->add(self::SCHOOL_YEAR_ID, $school_year->getId());
     }
     return self::doSelectOne($c);
 }