@property
    def duration(self):
        """
        Return the duration (in milliseconds) that this item was in-progress.
        """
        if self.date_started and self.date_finished:
            duration = (self.date_started - self.date_finished).total_seconds() * 1000
        else:
            duration = None
        return duration
dataset/ETHPy150Open dropbox/changes/changes/models/jobstep.py/JobStep.duration/swapped operands of `-`