The spec for this action:
https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf#G11.2111850
An example of a form using this action:
https://www2.illinois.gov/rev/forms/reg/Documents/reg-1-mr.pdf
const obj = this._catDict.get("Names");
    let xfaImages = null;
    if (obj instanceof Dict && obj.has("XFAImages")) {
      const nameTree = new NameTree(obj.getRaw("XFAImages"), this.xref);
      for (const [key, value] of nameTree.getAll()) {
        if (!xfaImages) {
          xfaImages = new Dict(this.xref);
        }
        xfaImages.set(key, value);
      }
    }
    return shadow(this, "xfaImages", xfaImages);
  }
  _collectJavaScript() {
    const obj = this._catDict.get("Names");
    let javaScript = null;
    function appendIfJavaScriptDict(name, jsDict) {