This is part of a larger project which aims to integrate the Google Assistant SDK into Unreal Engine 4.
This particular section uses API.AI to communicate with the "Actions on Google" API. This is where the Google Assistant "talks" to API.AI, which in turn generates the "Intents" which determine what different voice commands do.
If you are implementing your own custom behaviors for the Google Assistant, you should create your own API.AI project and make your own version of the Javascript code contained within this project.