Solved by vinsent_paramanantha in post #3 
              
              
                Thank you @eqy 
But my question is about how to pick the top 3 max values of the indexes and store that indexes in a variable . This is a solution I found 
frame = sorted(range(len(mul_reward)), key=lambda i: mul_reward[i], reverse=True)[:4] 
print(frame) 
con_frame = torch.Tensor(frame)