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
this._items.forEach(({ displayValue }, i) => {
          if (values.has(displayValue)) {
            this._currentValueIndices.push(i);
          }
        });
      } else {
        this._currentValueIndices = this._items.findIndex(
          ({ displayValue }) => value === displayValue
        );
      }
    }
  }
  get valueAsString() {
    if (this._valueAsString === undefined) {
      this._valueAsString = this._value ? this._value.toString() : "";
    }
    return this._valueAsString;
  }
  set valueAsString(val) {
    this._valueAsString = val ? val.toString() : "";
  }
  browseForFileToSubmit() {
    if (this._browseForFileToSubmit) {
      
      
      
      this._browseForFileToSubmit();
    }
  }
  buttonGetCaption(nFace = 0) {