Draft: Refactor and implement API version of the worker

Closes #17

worker_generic_training_dataset/__init__.py

@@ -156,14 +156,17 @@ class Extractor(DatasetWorker):
         """
         logger.info(f"Processing element ({element})")
 
+        polygon = element.polygon
+
         if isinstance(element, Element):
+            # SQL result
             image = element.image
-            polygon = element.polygon
             wk_version = get_object_id(element.worker_version)
             wk_run = get_object_id(element.worker_run)
         else:
+            # API result
+            polygon = json.dumps(polygon)
             image = element.zone.image
-            polygon = element.zone.polygon
             wk_version = (
                 element.worker_version
                 if hasattr(element, "worker_version")
@@ -229,7 +232,7 @@ class Extractor(DatasetWorker):
                 f"Linking element {cached_element.id} to dataset ({self.cached_dataset.id})"
             )
             with cache_database.atomic():
-                cached_element: CachedDatasetElement = CachedDatasetElement.create(
+                CachedDatasetElement.create(
                     id=uuid.uuid4(),
                     element=cached_element,
                     dataset=self.cached_dataset,