Fix unintended overwrite when saving models and update conda dependencies

[WenjieDu]

What does this PR do?

1. fixing Unintended saving success when model file already exists #515;
2. update conda dependency ai4ts;

Before submitting

• Was this discussed/approved via a GitHub issue? Please add a link to it if that's the case.
• I have commented my code, particularly in hard-to-understand areas.