code: def redirect(self):
          
  
          logger.info("--- In SSO Redirect ---")
          saml_msg = self.unpack_redirect()
  
          try:
              _key = saml_msg["key"]
              saml_msg = IDP.ticket[_key]
              self.req_info = saml_msg["req_info"]
              del IDP.ticket[_key]
          except KeyError:
              try:
                  self.req_info = IDP.parse_authn_request(saml_msg["SAMLRequest"],
                                                          BINDING_HTTP_REDIRECT)
              except KeyError:
                  resp = BadRequest("Message signature verification failure")
                  return resp(self.environ, self.start_response)
  
              _req = self.req_info.message
  
              if "SigAlg" in saml_msg and "Signature" in saml_msg:  # Signed
              # request
                  issuer = _req.issuer.text
                  _certs = IDP.metadata.certs(issuer, "any", "signing")
                  verified_ok = False
                  for cert in _certs:
                      if verify_redirect_signature(saml_msg, IDP.sec.sec_backend,
                                                   cert):
                          verified_ok = True
                          break
                  if not verified_ok:
                      resp = BadRequest("Message signature verification failure")
                      return resp(self.environ, self.start_response)
  
              if self.user:
                  if _req.force_authn:
                      saml_msg["req_info"] = self.req_info
                      key = self._store_request(saml_msg)
                      return self.not_authn(key, _req.requested_authn_context)
                  else:
                      return self.operation(saml_msg, BINDING_HTTP_REDIRECT)
              else:
                  saml_msg["req_info"] = self.req_info
                  key = self._store_request(saml_msg)
                  return self.not_authn(key, _req.requested_authn_context)
          else:
              return self.operation(saml_msg, BINDING_HTTP_REDIRECT)
docs: This is the HTTP-redirect endpoint