code: def find_issuer(self, cert):
          
  
          for entry in self:
              if entry.subject == cert.issuer:
                  if entry.key_identifier and cert.authority_key_identifier:
                      if entry.key_identifier == cert.authority_key_identifier:
                          return entry
                  else:
                      return entry
  
          raise LookupError('Unable to find the issuer of the certificate specified')
docs: Return the issuer of the cert specified, as defined by this path
  
          :param cert:
              An asn1crypto.x509.Certificate object to get the issuer of
  
          :raises:
              LookupError - when the issuer of the certificate could not be found
  
          :return:
              An asn1crypto.x509.Certificate object of the issuer