import torch 
The import numpy as np 

Def f (x) : 
Return the torch. Mean (x) 

X=torch. Tensor ([1, 4, 3, 4], requires_grad=True) 

Y=f (x) 
Y.b ackward () 
Print (x.g rad) 
Print (torch. Mean (x)) 

This is the title of vector derivation, why the result is:
Tensor ([0.2500, 0.2500, 0.2500, 0.2500])
Please explain