docs: def certificate_issuer(self, value):
          """
          An asn1crypto.x509.Certificate object of the issuer of the certificate.
          This should only be set if the OCSP responder is not the issuer of
          the certificate, but instead a special certificate only for OCSP
          responses.
          """
  
          if value is not None:
              is_oscrypto = isinstance(value, asymmetric.Certificate)
              if not is_oscrypto and not isinstance(value, x509.Certificate):
                  raise TypeError(_pretty_message(
                      '''
                      certificate_issuer must be an instance of
                      asn1crypto.x509.Certificate or
                      oscrypto.asymmetric.Certificate, not %s
                      ''',
                      _type_name(value)
                  ))
  
              if is_oscrypto:
                  value = value.asn1
  
          self._certificate_issuer = value