请问，下载sinaweibopy源码，在Eclipse工程中打开有第102行代码有问题出现错误。错误内容：”Undefined variable from import: types_map“，请问是怎么回事？

def _guess_content_type(url):

    n = url.rfind('.')

    if n==(-1):

        return 'application/octet-stream'

    ext = url[n:]

    return mimetypes.types_map.get(ext, 'application/octet-stream')