code: def _get_choices(self, gandi):
          
          iso_codes = []
          dc_codes = []
          for item in gandi.datacenter.list():
              iso_codes.append(item['iso'])
              if item.get('dc_code'):
                  dc_codes.append(item['dc_code'])
          return dc_codes + iso_codes
docs: Internal method to get choices list