fix comment

src/promptflow/promptflow/azure/_storage/cosmosdb/span.py

@@ -13,7 +13,6 @@
 
 
 class Span:
-
     name: str = None
     context: dict = None
     kind: str = None
@@ -71,16 +70,19 @@ def to_dict(self) -> Dict[str, Any]:
         return {k: v for k, v in self.__dict__.items() if v}
 
     def _persist_events(self, blob_container_client: ContainerClient, blob_base_uri: str):
-        idx = 0
-        for event in self.events:
+        if not blob_base_uri.endswith("/"):
+            blob_base_uri += "/"
+
+        for idx, event in enumerate(self.events):
             event_data = json.dumps(event)
             blob_client = blob_container_client.get_blob_client(self._event_path(idx))
             blob_client.upload_blob(event_data)
 
             event[SpanEventFieldName.ATTRIBUTES] = {}
             self.external_event_data_uris.append(f"{blob_base_uri}{self._event_path(idx)}")
 
-            idx += 1
+    EVENT_PATH_PREFIX = ".promptflow/.trace"
 
     def _event_path(self, idx: int) -> str:
-        return f".promptflow/.trace/{self.collection_id}/{self.context[SpanContextFieldName.TRACE_ID]}/{self.id}/{idx}"
+        trace_id = self.context[SpanContextFieldName.TRACE_ID]
+        return f"{self.EVENT_PATH_PREFIX}/{self.collection_id}/{trace_id}/{self.id}/{idx}"