{
    "error": true,
    "read_preference": {
        "maxStalenessSeconds": 1,
        "mode": "Nearest"
    },
    "topology_description": {
        "servers": [
            {
                "address": "a:27017",
                "type": "Unknown"
            },
            {
                "address": "b:27017",
                "type": "Unknown"
            }
        ],
        "type": "ReplicaSetNoPrimary"
    }
}