The type accepts mock, so it generates a nested object 
{
  "person_name": {
    "type": "firstName"
  },
  "phones": {
    "type": "mock",
    "params": {
      "repeat": 3,
      "mock": {
        "phone_number": {
          "type": "phoneNumber"
        }
      }
    }
  }
}
It returns 
{
  "person_name": "John",
  "phones": [
    {
      "phone_number": "447.116.3957"
    },
    {
      "phone_number": "1 (583) 480-8436"
    },
    {
      "phone_number": "1-583-422-1269"
    }
  ]
}