def provide_progress_saver(self, metrics_to_log):
        """
        Provide Progress Saver dictionary.

        Args:
            metrics_to_log: see __init__(). Describes the structure of Progress_Saver.
        """
        Progress_Saver = {
            key: {sub_key: [] for sub_key in metrics_to_log[key]}
            for key in metrics_to_log.keys()
        }
        return Progress_Saver

        Provide Progress Saver dictionary.

        Args:
            metrics_to_log: see __init__(). Describes the structure of Progress_Saver.
        
examples/pytorch/hilander/PSS/Smooth_AP/src/auxiliaries.py