I know this is simple and it's probably out there some where I'm just not sure what to look for "class inheritance"? I'm trying to access ship's `this` function from within cargo. Ideas?

```
var Ship = function() {
    this.id = Math.floor(Math.random() * 1000000);
};

var Cargo = function(){
    this.id = Math.floor(Math.random() * 1000000);
}

Cargo.prototype.push = function(string){
    return string;
}

Ship.prototype.cargo = Cargo;

module.exports = Ship;

```