Function cf

resources/vega-lite.min.js:7690–7701

(e)

      : "datum" === e.object.name;
  }
  function cf(e) {
    const n = t.parseExpression(e),
      i = new Set();
    return (
      n.visit((e) => {
        "MemberExpression" === e.type &&
          lf(e) &&
          i.add(sf(e).slice(1).join("."));
      }),
      i
    );
  }
  class uf extends $c {
    clone() {
      return new uf(null, this.model, l(this.filter));