static registerManager(scheme, manager) {
        (0, _util.assert)(scheme != null, ()=>"scheme must not be undefined or null.");
        if (scheme.endsWith(URL_SCHEME_SUFFIX)) scheme = scheme.slice(0, scheme.indexOf(URL_SCHEME_SUFFIX));
        (0, _util.assert)(scheme.length > 0, ()=>"scheme must not be an empty string.");
        const registry = ModelStoreManagerRegistry.getInstance();
        (0, _util.assert)(registry.managers[scheme] == null, ()=>`A model store manager is already registered for scheme '${scheme}'.`);
        registry.managers[scheme] = manager;
    }
Register a save-handler router.

@param saveRouter A function that maps a URL-like string onto an instance
of `IOHandler` with the `save` method defined or `null`.