declare namespace Ext {
    export namespace grid {
        export namespace feature {
            export interface GroupStoreConfig {
                listeners?: object;
            }

            export class GroupStore extends Ext.util.Observable  {
                public getById(id?: any): Ext.data.Model;
                public indexOfId(id?: string): number;
                public indexOfTotal(record?: Ext.data.Model): number;
            }
        }
    }
}