code: @InterfaceAudience.Private
      protected void checkSession() {
          if (getAuthenticator() != null) {
              Authorizer auth = (Authorizer) getAuthenticator();
              auth.setRemoteURL(remote);
              auth.setLocalUUID(db.publicUUID());
          }
          if (getAuthenticator() != null && getAuthenticator() instanceof SessionCookieAuthorizer) {
              // Sync Gateway session API is at /db/_session; try that first
              checkSessionAtPath("_session");
          } else {
              login();
          }
      }
docs: Before doing anything else, determine whether we have an active login session.