Question about the _attack function in sign_opt.py.

[d505]

Hello,
I have a question about the _attack function in sign_opt.py. In particular, I have a question about the area around line 536.
https://github.com/Trusted-AI/adversarial-robustness-toolbox/blob/main/art/attacks/evasion/sign_opt.py#L536

Why is it NOT MOVING if the alpha is less than le-4?
https://github.com/Trusted-AI/adversarial-robustness-toolbox/blob/main/art/attacks/evasion/sign_opt.py#L524
If I keep applying 0.25, won't it be less than le-4 even if I am successful?