code: def make_sign(api_secret, params=[]):
      
      _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()
docs: >>> make_sign("123456",[1,'2',u'中文'])
          '33C9065427EECA3490C5642C99165145'