Troubleshooting 'key is not defined' error when creating an object for a class with constructor in Fabcar.js

Question

I am adding a class with constructor in Fabcar.js and trying to create object for the class and call the constructor with new key word. But i am getting error like below.

" Failed to evaluate transaction: Error: key is not defined "

This is the code written in fabcar.js

const AES = class {
    constructor(key) {
        if (!(this instanceof AES)) {
            throw Error('AES must be instanitated with `new`');
        }
    
        Object.defineProperty(this, 'key', {
            value: this.callMethod(key, true)
        });
    
        this._prepare();
    }
};

class FabCar extends Contract { 
  async createDonorRegDetails(ctx,arg1,arg2) {
    // other code here

    var key = [
          84, 104,  97, 116, 115,
          32, 109, 121,  32,  75,
         117, 110, 103,  32,  70,
         117
       ];
      
       var aes = new AES(key);
   }
}

module.exports = FabCar;