code: def list_migration_choice(cls, datacenter):
          
          datacenter_id = cls.usable_id(datacenter)
          dc_list = cls.list()
          available_dcs = [dc for dc in dc_list
                           if dc['id'] == datacenter_id][0]['can_migrate_to']
          choices = [dc for dc in dc_list
                     if dc['id'] in available_dcs]
          return choices
docs: List available datacenters for migration from given datacenter.