code: def _session_key(self):
          
  
          if not hasattr(self, "_cached_session_key"):
              session_id_bytes = self.get_secure_cookie("session_id")
              session_id = None
  
              if session_id_bytes:
                  try:
                      session_id = session_id_bytes.decode('utf-8')
                  except:
                      pass
  
              if not session_id:
                  session_id = oz.redis_sessions.random_hex(20)
  
              session_time = oz.settings["session_time"]
              kwargs = dict(
                  name="session_id",
                  value=session_id.encode('utf-8'),
                  domain=oz.settings.get("cookie_domain"),
                  httponly=True,
              )
              if session_time:
                  kwargs["expires_days"] = round(session_time/60/60/24)
  
              self.set_secure_cookie(**kwargs)
  
              password_salt = oz.settings["session_salt"]
              self._cached_session_key = "session:%s:v4" % oz.redis_sessions.password_hash(session_id, password_salt=password_salt)
  
          return self._cached_session_key
docs: Gets the redis key for a session