'Returns all CourseOverview objects in the database.
Arguments:
orgs (list[string]): Optional parameter that allows case-insensitive
filtering by organization.
filter_ (dict): Optional parameter that allows custom filtering.'

@classmethod
def get_all_courses(cls, orgs=None, filter_=None):

    course_overviews = CourseOverview.objects.all()
    if orgs:
        course_overviews = course_overviews.filter(org__iregex=(('(' + '|'.join(orgs)) + ')'))
    if filter_:
        course_overviews = course_overviews.filter(**filter_)
    return course_overviews
