read pickle compatibility with pandas 2

[0xd5dc]

Pandas 2.0.2 broke the backward compatibility with Pandas 1.x.
In i_o.py, from_pickle() used the pickle module to read pickle files that will raise ModuleNotFoundError: No module named 'pandas.core.indexes.numeric' error under Pandas 2.
A possible solution is to use pd.read_pickle() to read pickle files instead.

refs:
https://stackoverflow.com/questions/75953279/modulenotfounderror-no-module-named-pandas-core-indexes-numeric-using-metaflo