docs: def search_videos_by_keyword(self, keyword, category=None,
                                   period='week', orderby='relevance',
                                   public_type='all', paid=None,
                                   timeless=None, timemore=None,
                                   streamtypes=None,
                                   page=1, count=20):
          """doc: http://open.youku.com/docs/doc?id=81
          """
          url = 'https://openapi.youku.com/v2/searches/video/by_keyword.json'
          params = {
              'client_id': self.client_id,
              'keyword': keyword,
              'category': category,
              'period': period,
              'orderby': orderby,
              'public_type': public_type,
              'paid': paid,
              'timeless': timeless,
              'timemore': timemore,
              'streamtypes': streamtypes,
              'page': page,
              'count': count
          }
          params = remove_none_value(params)
          r = requests.get(url, params=params)
          check_error(r)
          return r.json()