fix: correct the position of import dpgen2 in tests

[wanghan-iapcm]

try to skip isort when the relative order of import is critical

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (66a5acc) 88.12% compared to head (c0ee9a2) 88.12%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #171 +/- ## ======================================= Coverage 88.12% 88.12% ======================================= Files 80 80 Lines 4032 4032 ======================================= Hits 3553 3553 Misses 479 479 ```

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