def _newer(a: str, b: str) -> bool:
    """Inquire whether file a was written since file b."""
    if not os.path.exists(a):
        return False
    if not os.path.exists(b):
        return True
    return os.path.getmtime(a) >= os.path.getmtime(b)
Inquire whether file a was written since file b.
src/blib2to3/pgen2/driver.py