Hi I get the following error for my below code for this exercise:

TypeError: ‘int’ object is not iterable

```
#Write your function here
def append_sum(lst):
first_sum = sum(lst[-1] +lst[-2])
lst.append(first_sum)
second_sum = sum(lst[-1] +lst[-2])
lst.append(second_sum)
third_sum = sum(lst[-1] +lst[-2])
lst.append(third_sum)
return lst
#Uncomment the line below when your function is done
print(append_sum([1, 1, 2]))
```

Is this because the lst parameter is not updated until the entire function code is finished executing?