Help on error: Vars can be assigned only at root when grouped by Value

Users Dgraph
3

Edge.

{
  film (func: has(genre)) {
    uid
    name
    genre {
      uid
      name
    }
  }
}

{
  "data": {
    "film": [
      {
        "uid": "0x30d41",
        "name": "Toy Story (1995)",
        "genre": {
          "uid": "0x186a3",
          "name": "Animation"
        }
      },
      {
        "uid": "0x30d42",
        "name": "GoldenEye (1995)",
        "genre": {
          "uid": "0x186a1",
          "name": "Action"
        }
      },
      {
        "uid": "0x30d43",
        "name": "Four Rooms (1995)",
        "genre": {
          "uid": "0x186b0",
          "name": "Thriller"
        }
      },
...