has(key) {
    return Boolean(this.store.getState()[0][key]);
  }
@method has
@instance
@description Returns whether manager has a dependency with the given key
@param {String} key the key of the dependency
@memberof module:core.ModuleManager
@return {Boolean} Promise that is resolved when all promises completed.
@example <caption>Check whether the store has the 'hello' dependency</caption>
manager.has('hello'); // -> true