[
  {
    "a": "a",
    "foo": [
      {
        "$numberInt": "1"
      },
      {
        "$numberInt": "2"
      },
      {
        "$numberInt": "3"
      }
    ],
    "z": "z",
    "notes": "foo is an array of simple values"
  },
  {
    "a": "a",
    "foo": [
      {
        "$numberInt": "1"
      }
    ],
    "z": "z",
    "notes": "foo is not always of the same length"
  }
]