How to get the primitive associated with an entity?

CesiumJS
1

Entity API is very convenient and powerful but sometimes primitives give more options and flexibility.
For example, we can control animations for primitive models through a ModelAnimationCollection, we can position a label primitive more precisely through label position property.

Before Cesium version 1.26 I used such routine to get to a label primitive associated with an entity.
Two stages - 1) finding a LabelCollection in a Scene PrimitivesCollection. and then 2) finding a right label by a reference to an entity

function getLabelForEntity(entity) {
    var primitives = viewer.scene.primitives;
    var primitive;
    for (var i = 0; i < primitives.length; i++) {
        primitive = primitives.get(i);
        if (primitive instanceof Cesium.LabelCollection) {
            var labelCollection = primitive;

            if (!labelCollection) return undefined;
            var label;
            for (var j = 0; j < labelCollection.length; j++) {
                label = labelCollection.get(j);
                if (label instanceof Cesium.Label && label.id === entity) {
                    return label;
                }
            }

        }
    }
    return undefined;
};

Something similar was recommended in this forum for models

function getModelForEntity(entity) {
    var primitives = viewer.scene.primitives;
    var primitive;

    for (var i = 0; i < primitives.length; i++) {
        primitive = primitives.get(i);
        if (primitive instanceof Cesium.Model && primitive.id === entity) {
            return primitive;
        }
    }
};

This approach (at least for Labels and Billboards) doesn’t work after introduction of EntityCluster in v.1.26
I can adopt my routines, but before doing that I’d like to ask if I’m doing a wrong thing and is there an other way to get to the needed primitive in an entity?

Thank you,
Vladimir.