bug fix to create event based on the type

if obs id and event id is the same for different types, the code failed.

dl1_data_handler/loader.py

@@ -149,7 +149,7 @@ def __getitem__(self, index):
                 )
         elif self.DLDataReader.mode == "stereo":
             batch = self.DLDataReader.generate_stereo_batch(batch_indices)
-            batch_grouped = batch.group_by(["obs_id", "event_id", "tel_type_id"])
+            batch_grouped = batch.group_by(["obs_id", "event_id", "tel_type_id", "true_shower_primary_class"])
             features = []
             true_shower_primary_class = []
             log_true_energy = []