parentCourseGroup.checkDuplicateChildNames(getName(), getNameEn());
    public Context addContext(CourseGroup parentCourseGroup, CurricularPeriod curricularPeriod,            ExecutionPeriod beginExecutionPeriod, ExecutionPeriod endExecutionPeriod) {        checkContextsFor(parentCourseGroup, curricularPeriod);        return new Context(parentCourseGroup, this, curricularPeriod, beginExecutionPeriod, endExecutionPeriod);    }