fix mkdir

[jiaqima]

Description

Changed os.mkdir(...) to os.makedirs(..., exist_ok=True) to fix the bug when pretrained folder already exists.

Together with commit da70155 by @chirag126, this should fix #4.

Test

Tested locally by running python openxai/api.py.

Also tested locally by running the following piece of code outside the OpenXAI folder:

from openxai.api import OpenXAI
oxai = OpenXAI(data_name="german", model_name="ann", explainer_name="lime")
df_full = oxai.query()
print(df_full.head())

and obtained the following outputs:

   duration    amount  installment-rate  ...  label  prediction  is_test
0  0.205882  0.228094          0.666667  ...    0.0         1.0      0.0
1  0.294118  0.072564          1.000000  ...    1.0         1.0      0.0
2  0.294118  0.064395          1.000000  ...    1.0         1.0      0.0
3  0.470588  0.355607          1.000000  ...    1.0         1.0      0.0
4  0.470588  0.421916          1.000000  ...    1.0         1.0      0.0

[5 rows x 123 columns]