```
def only_upper(t):
    res = []
    for s in t:
        if s.isupper():
            res.append(s)
        return res
t = ['a', 'B', 'c', 'D']

print only_upper(t)

```

I'm trying to figure out why this is returning an empty list. The result looks like this in the console: 

```
[]

```