Actually, the input I wrote here was pre-processed with underthesea · PyPI. The original input is … thị trấn An Phú, Huyện An phútỉnh An Giang
I do really appreciate your discussion.
According to the HuggingFace’s noted,

@HuggingFace is 3 (indexing B-corporation ), we would set the labels of ['@', 'hugging', '##face'] to [3, -100, -100] .

So, I think it would be more precise with the following tags,

Thi_trấn,  ‘an_@@’,   ‘phú’,    huyện,    an,         ‘phú@@’,   ‘tỉnh’,     ‘an_@@’,    ‘giang’’
“B-LOC”, “I-LOC”, None, “I-LOC”, “I-LOC”, “I-LOC”, None, “I-LOC”, None

In their document, they also declared that the labels we wish to ignore to -100 (labelled as None) .