@classmethod
def find_spec(cls, fullname, path=None, target=None):
    """Try to find a spec for 'fullname' on sys.path or 'path'.

    The search is based on sys.path_hooks and sys.path_importer_cache.
    """
    if path is None:
        path = sys.path
    spec = cls._get_spec(fullname, path, target)
    '''
    後略...
    '''