sdk/lib/_internal/allowed_experiments.json

{
  "version": 1,
  "experimentSets": {
    "sdkExperiments": []
  },
  "sdk": {
    "default": {
      "experimentSet": "sdkExperiments"
    },
    "_example_libraries": {
      "ui": {
        "experimentSet": "nullSafety"
      }
    }
  },
  "packages": {}
}