I am having a hard time understanding Python.. can somebody please tell me what I am doing wrong and explain to me why it is not working?

Here is the assignment:

Define a function called list_extender that has one parameter lst.

Inside the function, append the number 9 to lst.

Then return the modified list.

Here is my code:

```
n = [3, 5, 7]
# Add your function here
def list_extender(1st):
n.append(9)
return n
print list_extender(n)
```

Thank you in advance.