fix: revert class attributes removal

Signed-off-by: Yves Bastide <yves@botify.com>

Author: ybastide

simpleflow/swf/mapper/models/event/base.py

@@ -42,6 +42,7 @@ class Event:
     :param  raw_data: raw_event representation provided by amazon service
     """
 
+    # These class attributes manipulate instance ones
     _type: str | None = None
     _name: str | None = None
     _attributes_key: str | None = None