export type ValueFn<T extends BaseType, Datum, Result> = (this: T, datum: Datum, index: number, groups: T[] | ArrayLike<T>) => Result;

attrTween(name: string): ValueFn<GElement, Datum, (t: number) => string> | undefined;

caller.attrTween("points", (d, index, groups) => { return (t) => {return "";};  }

caller is Transition<BaseType, PieArcDatum<number>

(parameter) d: d3.PieArcDatum<number>
(parameter) index: number
(parameter) groups: d3.BaseType[] | d3.ArrayLike<d3.BaseType>