prefix transform bug?

[sersh88]

In prefix transform I see the code to prepend prefix:

 def _prepend(self, example, prefix):
        """Prepend `prefix` to `tokens`."""
        for side, side_prefix in prefix.items():
            if example.get(side) is not None:
                example[side] = side_prefix.split(" ") + example[side]
            elif len(side_prefix) > 0:
                example[side] = side_prefix.split(" ")
        return example

Looks like it prepends prefix even if it's empty. I think it should be like:

 def _prepend(self, example, prefix):
        """Prepend `prefix` to `tokens`."""
        for side, side_prefix in prefix.items():
            if example.get(side) is not None and len(side_prefix) > 0:
                example[side] = side_prefix.split(" ") + example[side]
            elif len(side_prefix) > 0:
                example[side] = side_prefix.split(" ")
        return example

[vince62s]

what is the issue exactly ?

[sersh88]

if tgt_prefix, for example, is empty, the transform anyways adds empty token to each tgt sequence, which is unknown token for the model. So, all dataset is trained with prepended unknown token to tgt. like ['', 'some', 'other', 'tokens'] Same with suffix transform.

[vince62s]

I see, can you PR?