Fix imports for Model Customization interfaces (#5832)

Author: aviruthen

sagemaker-train/src/sagemaker/train/__init__.py

@@ -28,6 +28,24 @@ def __getattr__(name):
     elif name == "ModelTrainer":
         from sagemaker.train.model_trainer import ModelTrainer
         return ModelTrainer
+    elif name == "SFTTrainer":
+        from sagemaker.train.sft_trainer import SFTTrainer
+        return SFTTrainer
+    elif name == "DPOTrainer":
+        from sagemaker.train.dpo_trainer import DPOTrainer
+        return DPOTrainer
+    elif name == "RLVRTrainer":
+        from sagemaker.train.rlvr_trainer import RLVRTrainer
+        return RLVRTrainer
+    elif name == "RLAIFTrainer":
+        from sagemaker.train.rlaif_trainer import RLAIFTrainer
+        return RLAIFTrainer
+    elif name == "TrainingType":
+        from sagemaker.train.common import TrainingType
+        return TrainingType
+    elif name == "CustomizationTechnique":
+        from sagemaker.train.common import CustomizationTechnique
+        return CustomizationTechnique
     elif name == "logger":
         from sagemaker.core.utils.utils import logger
         return logger