Exclude classes from inference using pretrained or custom models

[gguzzy]

Hello dear all,
I am writing you to share and open a PR to include in your framework the option to exclude certain classes from inferences/predictions performed, since I found this useful in general.

This allows us to exclude predictions which are not considered by a custom user.

This can be done by using two new optional parameters which are: exclude_classes_names and exclude_classes_id.

Recall to use the same notation for class names and ids accordingly to the loaded model.

I introduced an example which shows the usage of the new parameter, added to folder tests as test_exclude_classes.py'

The methods which include the new parameters are the ones which are responsible for predictions, which are 'prediction, get_sliced_prediction, get_prediction' and their respective usages inside the 'predict.py' class.

[gguzzy]

The only one thing missing is adding these new parameters into the methods definitions (the comments explaining the parameters, and not adding it to the method as parameter, which has been already done), it is not such a huge issue to deal with. Waiting for your review and approval.

[gguzzy]

I updated the code and workflow also using both black and isort. Waiting for your approval.