Comment alignment when `spaces_before_comment` is a list

Hey all!

I've just started using yapf with hopes for making easier the burden of code-cleanup.

I very much like the aesthetics of aligned comments when it comes to blocks of code, but having a list of values in `spaces_before_comment` kinda creates problems when I have blocks with comments on the side, as well as commented out lines.

I can imagine comments and commented out lines within a block are hard to distinguish programmatically, but is there something in yapf that would allow for not having the problem, where:

```
from torch.utils.data import DataLoader # this is an important comment
import numpy as np
# import torch
import matplotlib.pyplot as plt
# import sounddevice as sd
# import os
# import torchaudio
```

gets corrected to:

```
from torch.utils.data import DataLoader # this is an important comment
import numpy as np
# import torch
import matplotlib.pyplot as plt
# import sounddevice as sd
# import os
# import torchaudio
```

Thank you in advance!