Draft: Refactor and implement API version of the worker

Closes #17

worker_generic_training_dataset/from_api.py

 # -*- coding: utf-8 -*-
 from uuid import UUID
 
+from arkindex_worker.models import MagicDict
 from arkindex_worker.worker.classification import ClassificationMixin
 from arkindex_worker.worker.element import ElementMixin
 from arkindex_worker.worker.entity import EntityMixin
@@ -18,10 +19,11 @@ class DatasetExtractorFromAPI(
     MetaDataMixin,
 ):
     def list_classifications(self, element_id: UUID):
-        return iter(
+        return map(
+            MagicDict,
             self.api_client.request("RetrieveElement", id=str(element_id))[
                 "classifications"
-            ]
+            ],
         )