'Return a list of regions objects the app is available in, e.g.:
[<class \'mkt.constants.regions.GBR\'>,...]
if `regions` is provided we\'ll use that instead of calling
self.get_region_ids()'

def get_regions(self, regions=None, sort_by='slug'):

    regions_ids = (regions or self.get_region_ids(restofworld=True))
    _regions = map(mkt.regions.REGIONS_CHOICES_ID_DICT.get, regions_ids)
    return sorted(_regions, key=operator.attrgetter(sort_by))
