code: def get_index_list(self, as_json=False):
          
  
          url = self.index_url
          req = Request(url, None, self.headers)
          # raises URLError or HTTPError
          resp = self.opener.open(req)
          resp = byte_adaptor(resp)
          resp_list = json.load(resp)['data']
          index_list = [str(item['name']) for item in resp_list]
          return self.render_response(index_list, as_json)
docs: get list of indices and codes
          params:
              as_json: True | False
          returns: a list | json of index codes