Attempt to fix nested model retrival

opensensor/collection_apis.py

@@ -203,7 +203,6 @@ def create_nested_pipeline(model: Type[BaseModel], prefix="", pipeline=None):
     match_conditions = {}
     if pipeline is None:
         pipeline = {
-            "_id": False,
             "timestamp": "$timestamp",
         }
 
@@ -397,11 +396,13 @@ def get_uniform_sample_pipeline(
                     }
                 }
             }
+            # Add a stage to explicitly exclude _id field from the output
         },
         {"$group": {"_id": "$group", "doc": {"$first": "$$ROOT"}}},
         {"$replaceRoot": {"newRoot": "$doc"}},
         {"$project": project_pipeline},
         {"$sort": {"timestamp": 1}},
+        {"$project": {"_id": 0}},
     ]
 
     logger.info(f"Pipeline for {response_model.__name__}: {pipeline}")