How to use the brotli/decompress function in brotli

_decompress() {
    // decompress data and setup table offsets if we haven't already
    if (!this._decompressed) {
      this.stream.pos = this._dataPos;
      let buffer = this.stream.readBuffer(this.directory.totalCompressedSize);

      let decompressedSize = 0;
      for (let tag in this.directory.tables) {
        let entry = this.directory.tables[tag];
        entry.offset = decompressedSize;
        decompressedSize += (entry.transformLength != null) ? entry.transformLength : entry.length;
      }

      let decompressed = brotli(buffer, decompressedSize);
      if (!decompressed) {
        throw new Error('Error decoding compressed data in WOFF2');
      }

      this.stream = new r.DecodeStream(new Buffer(decompressed));
      this._decompressed = true;
    }
  }