I have a function f(featureList) that takes a list of arbitrary length as input and gives another list of the same length as output

And I have a pandas dataframe that looks like

Class_ID  Date           Student_ID      feature  
1         1/1/2023       3               0.02167131     
1         1/1/2023       4               0.17349148     
1         1/1/2023       6               0.08438952     
1         1/1/2023       8               0.04143787     
1         1/1/2023       9               0.02589056
1         1/1/2023       1               0.03866752     
1         1/1/2023       10              0.0461553                                   
3         17/4/2022      5               0.2     
3         17/4/2022      2               0.1     
3         17/4/2022      3               0.55     
3         17/4/2022      4               0.15     

and I would like to apply the function f(featureList) to the feature column groupby Class_ID and generate a new column called New_feature. And here’s my code:

df['New_feature'] = df.groupby('Class_ID', group_keys=False)['feature'].apply(f)

However it gives the following error:

KeyError: 0

The above exception was the direct cause of the following exception: 
# If we have a listlike key, _check_indexing_error will raise```