fromisoformat is too new

piket_client/model.py

     @classmethod
     def from_dict(cls, data: dict) -> "Consumption":
         """ Reconstruct a Consumption from a dict. """
+        datetime_format = '%Y-%m-%dT%H:%M:%S.%f'
+        # 2018-08-31T17:30:47.871521
         return cls(
             consumption_id=data["consumption_id"],
             person_id=data["person_id"],
             consumption_type_id=data["consumption_type_id"],
             settlement_id=data["settlement_id"],
-            created_at=datetime.datetime.fromisoformat(data["created_at"]),
+            created_at=datetime.datetime.strptime(data["created_at"],
+                datetime_format),
             reversed=data["reversed"],
         )