The usage of '<oov>' is not consistent with the paper #39

In paper, the importance score of the word is calculated by removing this word, but you use '<oov>' to replace this word to calculate the importance score in
https://github.com/jind11/TextFooler/blob/master/attack_classification.py#L216

Moreover, the '<oov>' will be tokenized into 4 tokens which may have attention affects with other words.
I'm wondering why such nonsensical '<oov>' is used?