I am trying to delete a list within a list but my code is unable to do so even though I have deleted the list. 

```
y = [45]  
x = [1,2,3,5,y]    

del y        
print(x)

```

Output of printing x:

```
[1, 2, 3, 5, [45]]

```

My output shows as `[1, 2, 3, 5, [45]]` which means list `y` still exists in list `x`.  

But I deleted list `y` in my code. Why is list `y` still not deleted then? Is there something wrong with my code? How do I delete an entire list in Python?