Re-export ImputationMode at study level

Author: kalama-ai

octopus/study/types.py

@@ -1,4 +1,5 @@
 """Study types."""
 
-# ImputationMethod has been moved to octopus/types.py
-# Import it from there if needed: from octopus.types import ImputationMethod
+from octopus.types import ImputationMethod
+
+__all__ = ["ImputationMethod"]