def METHOD_NAME(cls, v, values):
    if v is None:
        cluster_type = values["type"]
        default_thumbnails = {
            ClusterTypeInModel.AWS.value: "https://upload.wikimedia.org/wikipedia/commons/thumb/9/93/Amazon_Web_Services_Logo.svg/250px-Amazon_Web_Services_Logo.svg.png",
            ClusterTypeInModel.ON_PREMISE.value: "https://upload.wikimedia.org/wikipedia/commons/thumb/a/ac/Crystal_Clear_app_network_local.png/120px-Crystal_Clear_app_network_local.png",
        }
        return default_thumbnails[cluster_type]
    return v