$pickSet
Takes an array and a number quantity and returns a new n-element array containing unique values from the input array.
Optionally picks with probability proportional to a provided weights array.
Options¶
- from(required) Array of values or operators to choose from.
- quantity(optional) The size of the output array. Default- 1.
- weights(optional) Array of weightings (must be the same length as- array).
Example¶
{
    "color": {
        "$pickSet": {
            "from": ["green", "red", "blue"],
            "quantity": 2
        }
    }
}
{
    "color": ["red", "green"]
}