How to use the martinez-polygon-clipping.union function in martinez-polygon-clipping

Offset.prototype.offsetContour = function(curve, edges) {
  var union, i, len;
  if (isArray(curve[0]) && typeof curve[0][0] === 'number') {
    // we have 1 less edge than vertices
    for (i = 0, len = curve.length - 1; i < len; i++) {
      var segment = this.ensureLastPoint(
        this._offsetSegment(curve[i], curve[i + 1], edges[i], this._distance)
      );
      union = (i === 0) ?
                [this.ensureLastPoint(segment)] :
                martinez.union(union, this.ensureLastPoint(segment));
    }
  } else {
    for (i = 0, len = edges.length; i < len; i++) {
      union = (i === 0) ?
        this.offsetContour(curve[i], edges[i]) :
        martinez.union(union, this.offsetContour(curve[i], edges[i]));
    }
  }
  return union;
};

var union, i, len;
  if (isArray(curve[0]) && typeof curve[0][0] === 'number') {
    // we have 1 less edge than vertices
    for (i = 0, len = curve.length - 1; i < len; i++) {
      var segment = this.ensureLastPoint(
        this._offsetSegment(curve[i], curve[i + 1], edges[i], this._distance)
      );
      union = (i === 0) ?
                [this.ensureLastPoint(segment)] :
                martinez.union(union, this.ensureLastPoint(segment));
    }
  } else {
    for (i = 0, len = edges.length; i < len; i++) {
      union = (i === 0) ?
        this.offsetContour(curve[i], edges[i]) :
        martinez.union(union, this.offsetContour(curve[i], edges[i]));
    }
  }
  return union;
};

Offset.prototype.offsetContour = function(curve, edges) {
  var union, i, len;
  if (isArray(curve[0]) && typeof curve[0][0] === 'number') {
    // we have 1 less edge than vertices
    for (i = 0, len = curve.length - 1; i < len; i++) {
      var segment = this.ensureLastPoint(
        this._offsetSegment(curve[i], curve[i + 1], edges[i], this._distance)
      );
      union = (i === 0) ?
                [this.ensureLastPoint(segment)] :
                martinez.union(union, this.ensureLastPoint(segment));
    }
  } else {
    for (i = 0, len = edges.length; i < len; i++) {
      union = (i === 0) ?
        this.offsetContour(curve[i], edges[i]) :
        martinez.union(union, this.offsetContour(curve[i], edges[i]));
    }
  }
  return union;
};

var union, i, len;
  if (isArray(curve[0]) && typeof curve[0][0] === 'number') {
    // we have 1 less edge than vertices
    for (i = 0, len = curve.length - 1; i < len; i++) {
      var segment = this.ensureLastPoint(
        this._offsetSegment(curve[i], curve[i + 1], edges[i], this._distance)
      );
      union = (i === 0) ?
                [this.ensureLastPoint(segment)] :
                martinez.union(union, this.ensureLastPoint(segment));
    }
  } else {
    for (i = 0, len = edges.length; i < len; i++) {
      union = (i === 0) ?
        this.offsetContour(curve[i], edges[i]) :
        martinez.union(union, this.offsetContour(curve[i], edges[i]));
    }
  }
  return union;
};

Offset.prototype.margin = function(dist) {
  this.distance(dist);

  if (typeof this.vertices[0] === 'number') { // point
    return this.offsetPoint(this._distance);
  }

  if (dist === 0) return this.vertices;

  var union = this.offsetLines(this._distance);
  //return union;
  union = martinez.union(this.vertices, union);
  return orientRings(union);
};

Offset.prototype.margin = function(dist) {
  this.distance(dist);

  if (typeof this.vertices[0] === 'number') { // point
    return this.offsetPoint(this._distance);
  }

  if (dist === 0) return this.vertices;

  var union = this.offsetLines(this._distance);
  //return union;
  union = martinez.union(this.vertices, union);
  return orientRings(union);
};

}

                // Generate some unique IDs and add some metadata
                var featurehash = utilHashcode(stringify(feature));
                var propertyhash = utilHashcode(stringify(feature.properties || {}));
                feature.__layerID__ = layerID.replace(/[^_a-zA-Z0-9\-]/g, '_');
                feature.__featurehash__ = featurehash;
                feature.__propertyhash__ = propertyhash;
                features.push(feature);

                // Clipped Polygons at same zoom with identical properties can get merged
                if (isClipped && geometry.type === 'MultiPolygon') {
                    var merged = mergeCache[propertyhash];
                    if (merged && merged.length) {
                        var other = merged[0];
                        var coords = martinez.union(
                            feature.geometry.coordinates, other.geometry.coordinates
                        );

                        if (!coords || !coords.length) {
                            continue;  // something failed in martinez union
                        }

                        merged.push(feature);
                        for (var j = 0; j < merged.length; j++) {      // all these features get...
                            merged[j].geometry.coordinates = coords;   // same coords
                            merged[j].__featurehash__ = featurehash;   // same hash, so deduplication works
                        }
                    } else {
                        mergeCache[propertyhash] = [feature];
                    }
                }

.add('w8r', () => {
    w8r.union(
      holeHole.features[0].geometry.coordinates,
      holeHole.features[1].geometry.coordinates
    )
  })
  .run()