def _get_skip_class_names(skip_class_map):
    """Returns list of class names to skip

    Returned list only contains names of classes where all methods are skipped.
    If skip_class_map is None, returns None

    :param skip_class_map: Result of passing parsed arg for --skip command line
        argument to parse_test_names()

    :return: List of class names to skip
    """
    if skip_class_map:
        return [
            class_name for class_name, methods in skip_class_map.items() if not methods
        ]
    return None