Getting class gradient not found while running other attacks except hop_skip_jump

[ghousethanedar]

counterfit> set_target digits_mlp
digits_mlp> set_attack newtonfool
[+] success: Using 0e34bf51
digits_mlp>NewtonFool:0e34bf51> run
NewtonFool: 0%| | 0/1 [00:00<?, ?it/s]
[!] failed: Failed to run 0e34bf51 (art.attacks.evasion.newtonfool.NewtonFool): 'BlackBoxClassifier' object has no attribute
'class_gradient'

[ghousethanedar]

Any help for the above issue would be appreciated