'Deletes the requested grades in the given model, filtered by the provided args and kwargs.'

def _delete_grades(self, grade_model_class, *args, **kwargs):

    grades_query_set = grade_model_class.query_grades(*args, **kwargs)
    num_rows_to_delete = grades_query_set.count()
    log.info('reset_grade:    Deleting    %s:    %d    row(s).', grade_model_class.__name__, num_rows_to_delete)
    grade_model_class.delete_grades(*args, **kwargs)
    log.info('reset_grade:    Deleted    %s:    %d    row(s).', grade_model_class.__name__, num_rows_to_delete)
