get _pdfFunctionFactory() {
    const pdfFunctionFactory = new PDFFunctionFactory({
      xref: this.xref,
      isEvalSupported: this.options.isEvalSupported,
    });
    return shadow(this, "_pdfFunctionFactory", pdfFunctionFactory);
  }
Since Functions are only cached (locally) by reference, we can share one
`PDFFunctionFactory` instance within this `PartialEvaluator` instance.