New lines in templates

Im having trouble with new lines and empty lines when writing templates for mason.

For example:

Given `a` is `false` and `b` is `false`

Desired Output:
Empty file.

Given `a` is `false` and `b` is `true`

Desired Output:
```
B
```

Given `a` is `true` and `b` is `false`

Desired Output:
```
A
```

Given `a` is `true` and `b` is `true`

Desired Output:
```
A
B
```

How would the template of this scenario look like?