'Return a list of region objects the website is preferred in, e.g.::
[<class \'mkt.constants.regions.GBR\'>, ...]'

def get_preferred_regions(self, sort_by='slug'):

    _regions = map(mkt.regions.REGIONS_CHOICES_ID_DICT.get, self.preferred_regions)
    return sorted(_regions, key=operator.attrgetter(sort_by))
