AcroFormXObject = function AcroFormXObject() {
  AcroFormPDFObject.call(this);
  Object.defineProperty(this, "Type", {
    value: "/XObject",
    configurable: false,
    writable: true
  });
  Object.defineProperty(this, "Subtype", {
    value: "/Form",
    configurable: false,
    writable: true
  });
  Object.defineProperty(this, "FormType", {
    value: 1,
    configurable: false,
    writable: true
  });
  var _BBox = [];
  Object.defineProperty(this, "BBox", {
    configurable: false,
    get: function get() {
      return _BBox;
    },
    set: function set(value) {
      _BBox = value;
    }
  });
  Object.defineProperty(this, "Resources", {
    value: "2 0 R",
    configurable: false,
    writable: true
  });

  var _stream;

  Object.defineProperty(this, "stream", {
    enumerable: false,
    configurable: true,
    set: function set(value) {
      _stream = value.trim();
    },
    get: function get() {
      if (_stream) {
        return _stream;
      } else {
        return null;
      }
    }
  });
}
Returns an key-value-List of all non-configurable Variables from the Object

@name getKeyValueListForStream
@returns {string}