>>> make_sign("123456",[1,'2',u'中文'])
        '33C9065427EECA3490C5642C99165145'

def make_sign(api_secret, params=[]):
    """
        >>> make_sign("123456",[1,'2',u'中文'])
        '33C9065427EECA3490C5642C99165145'
    """
    _params = [utils.safeunicode(p) for p in params if p is not None]
    _params.sort()
    # print 'sorted params:',_params
    _params.insert(0, api_secret)
    strs = ''.join(_params)
    # print 'sign params:',strs
    mds = md5(strs.encode('utf-8')).hexdigest()
    return mds.upper()