Make collection_id an optional field

dma_client/models.py

@@ -46,7 +46,7 @@ class Data(DMABaseModel):  # pylint:disable=R0903
     comment: Optional[str]
     created: datetime
     data_type: str = Field(..., alias='type')
-    collection_id: int = Field(..., alias='collectionId')
+    collection_id: Optional[int] = Field(..., alias='collectionId')
     status: Optional[BasicDataStatus]