Looking at the paper, I found that many objects are preceded by many passive forms.
比如：The tokens are joined with underscores.
tokens are nouns and are used as objects here
join is a predicate verb
with underscores is a mode adverbial
Straightforward words: these words are concatenated with underscores
The mode adverbial here is used to modify the predicate verb,
According to Chinese main-predicate-guest translation:
"We use underscores to connect these words "