async

    return new Promise(async (resolve, reject) => {
      try {
        const depnString = JSON.stringify(this.depn);
        await fs.writeFile(path.join(this.dest, this.fileName), depnString);
      } catch (err) {
        reject(err);
      }
    });


TypeError [ERR_INVALID_CALLBACK]: Callback must be a function. Received undefined
    at maybeCallback (fs.js:142:9)
    at Object.writeFile (fs.js:1175:14)
    at /Users/myroot/Note/Node/The-Complete-Node.js-Developer-Course-3rd-Edition/node-course/depn/index.js:33:18
    at new Promise (<anonymous>)
    at app.write (/Users/myroot/Note/Node/The-Complete-Node.js-Developer-Course-3rd-Edition/node-course/depn/index.js:30:12)
    at Object.<anonymous> (/Users/myroot/Note/Node/The-Complete-Node.js-Developer-Course-3rd-Edition/node-course/depn-usage/app.js:5:6)
    at Module._compile (internal/modules/cjs/loader.js:776:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:787:10)
    at Module.load (internal/modules/cjs/loader.js:643:32)
    at Function.Module._load (internal/modules/cjs/loader.js:556:12)