I have this object which also contains arrays and objects and which is currently grouped by "category"

```
data = {
  vehicles: [
    {
      name: "Team1",
      cars: [
        {
          multiple: 0.5,
          category: "cars"
        },
        {
          multiple: 0.5,
          category: "cars"
        }
      ],
      bike: [
        {
          multiple: 0.5,
          category: "bike"
        }
      ],
      scooter: [
        {
          multiple: 0.5,
          category: "scooter"
        }
      ]
    },
    {
      name: "Team2",
      cars: [
        {
          multiple: 0.5,
          category: "cars"
        },
        {
          multiple: 0.5,
          category: "cars"
        }
      ],
      bike: [
        {
          multiple: 0.5,
          category: "bike"
        }
      ],
      scooter: [
        {
          multiple: 0.5,
          category: "scooter"
        }
      ]
    }
  ]
};

```

I used this line of code to groupby category but 

```
  return xs.reduce(function(rv, x) {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};
var data = groupBy(data, "category");

```

Since I have the object "data" now I want to perfrom further transformation
My question is it possible to groupby two categories so the output looks like this 

```
data = {
  vehicles: [
    {
      name: "Team1",
      cars: [
        {
          multiple: 0.5,
          category: "cars"
        },
        {
          multiple: 0.5,
          category: "cars"
        }
      ],
      bike_scooter: [
        {
          multiple: 0.5,
          category: "bike"
        },
        {
          multiple: 0.5,
          category: "scooter"
        }
      ]
    },
    {
      name: "Team2",
      cars: [
        {
          multiple: 0.5,
          category: "cars"
        },
        {
          multiple: 0.5,
          category: "cars"
        }
      ],
      bike_scooter: [
        {
          multiple: 0.5,
          category: "bike"
        },
        {
          multiple: 0.5,
          category: "scooter"
        }
      ]
    }
  ]
};

```