added abstract classes for torch propensity trainer

src/offline_rl_ope/PropensityModels/torch/Trainer.py

@@ -1,5 +1,5 @@
+from abc import abstractmethod
 import torch
-import torch.nn as nn
 import numpy as np
 import pickle
 
@@ -49,6 +49,25 @@ def save(self, path:str) -> None:
         if self.gpu:
             self.to_gpu()
 
+    @abstractmethod
+    def predict(
+        self, 
+        x:torch.Tensor, 
+        *args, 
+        **kwargs
+        ) -> torch.Tensor:
+        pass
+
+    @abstractmethod
+    def predict_proba(
+        self, 
+        x: torch.Tensor, 
+        y: torch.Tensor, 
+        *args, 
+        **kwargs
+        ) -> torch.Tensor:
+        pass
+
 
 
 class TorchClassTrainer(TorchPropensityTrainer):