code: def ocsp_url(self):
          
  
          if self._authority_information_access is None:
              return None
  
          for ad in self._authority_information_access:
              if ad['access_method'].native == 'ocsp' and ad['access_location'].name == 'uniform_resource_identifier':
                  return ad['access_location'].chosen.native
  
          return None
docs: Location of the OCSP responder for this certificate. Will be one of the
          following types:
  
           - None for no OCSP responder
           - A unicode string of the URL to the OCSP responder