code: def availability_zone_list(request):
      
      try:
          if api.cinder.extension_supported(request, 'AvailabilityZones'):
              return api.cinder.availability_zone_list(request)
          return []
      except Exception:
          exceptions.handle(request,
                            _('Unable to retrieve volumes availability zones.'))
          return []
docs: Utility method to retrieve a list of availability zones.