def download_img(fp, url, url_prefix=False):
    """Download_img need to test."""
    try:
        import subprocess
        if url_prefix:
            url = (
                'http://cq02-c1-vis-similar-bstmp1.cq02.baidu.com:8575/image/'
                 + url)
        shellcmd = (
            """
            wget --timeout={0} -t{1} -qO- "{2}" -O "{3}\""""
            .format(500, 3, url, fp))
        subprocess.getoutput(shellcmd)
        return fp
    except:
        return None
