code: def post(self):
          
          logger.info("--- In SSO POST ---")
          saml_msg = self.unpack_either()
          self.req_info = IDP.parse_authn_request(
              saml_msg["SAMLRequest"], BINDING_HTTP_POST)
          _req = self.req_info.message
          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_POST)
          else:
              saml_msg["req_info"] = self.req_info
              key = self._store_request(saml_msg)
              return self.not_authn(key, _req.requested_authn_context)
docs: The HTTP-Post endpoint