fix issue 868

[orange-crow]

fix issue #868;
according to pandas-dev/pandas#55008, pd.DataFrame.copy() leaks has been fixed by pandas 2.1.1

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.63%. Comparing base (fdf53ac) to head (d0dc267).
Report is 20 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1098      +/-   ##
==========================================
+ Coverage   81.62%   81.63%   +0.01%     
==========================================
  Files         248      248              
  Lines       13885    13885              
==========================================
+ Hits        11333    11335       +2     
+ Misses       2552     2550       -2     

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[geekan]

Since LLM does not actually use such a new version, although I think this may have some potential problems, since the problem has not been exposed yet, I merged it first.