Given:

`A = [['Yes', 'lala', 'No'], ['Yes', 'lala', 'Idontknow'], ['No', 'lala', 'Yes'], ['No', 'lala', 'Idontknow']]`

I want to know if `['Yes', X, 'No']` exist within A, where `X` is anything I don't care.

I attempted:

```
valid = False
for n in A:
    if n[0] == 'Yes' and n[2] == 'No':
        valid = True

```

I know `set()` is useful in this type of situations. But how can this be done? Is this possible? Or is it better for me to stick with my original code?