add support for n2p2 data format

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 83.08%. Comparing base (18a0ed5) to head (cfb6d7d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #627 +/- ## ========================================== + Coverage 82.81% 83.08% +0.27% ========================================== Files 73 74 +1 Lines 6580 6686 +106 ========================================== + Hits 5449 5555 +106 Misses 1131 1131 ```

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[Yi-FanLi]

could you add a test?

added by commit 506b187

[wanghan-iapcm]

@njzjz i merged it to master...