mpo dump remove warnings and future errors

[jiangtong1000]

Starting from numpy==1.24.0, the occurrence of the VisibleDeprecationWarning when trying to save a list of lists with varying lengths has been rectified, resulting in a ValueError instead. So I made some changes here.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (7a99b86) 85.26% compared to head (a6e4269) 85.27%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #152 +/- ## ======================================= Coverage 85.26% 85.27% ======================================= Files 105 105 Lines 9991 9995 +4 ======================================= + Hits 8519 8523 +4 Misses 1472 1472 ``` | [Impacted Files](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/152?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup) | Coverage Δ | | |---|---|---| | [renormalizer/mps/mp.py](https://app.codecov.io/gh/shuaigroup/Renormalizer/pull/152?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=shuaigroup#diff-cmVub3JtYWxpemVyL21wcy9tcC5weQ==) | `88.56% <100.00%> (+0.07%)` | :arrow_up: |

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[liwt31]

LGTM, thanks!