[Ablation] Develop a dataset generator function for databricks

[RiccardoGrigoletto]

As per https://github.com/logicalclocks/maggy/blob/master/maggy/ablation/ablationstudy.py , we need to write a custom function for the dataset generator to make AblationStudy to work on databricks.

[moritzmeister]

"There is one class that implements the AbstractAbletor class on maggy: LOCO. LOCO implements get_dataset_generator() that uses some hopsworks API to retrieve the datasets and so create the tf_dataset to use during training. We need to create a similar class that do that on databricks."