Function a

Returns
    | undefined
    | {
        ac: null;
        b: any;
        ctx: any;
        deps: null;
        f: number;
        first: null;
        fn: any;
        last: null;
        next: null;
        nodes_end: null;
        nodes_start: null;
        parent: any;
        prev: null;
        teardown: null;
        transitions: null;
        wv: number;
    }