We don't need to first check if the Dictionary contains the key, since trying to get a non-existent key simply returns `undefined` and we're already ensuring that the value is a boolean.
Furthermore, we shouldn't need to worry about the `Object.prototype` containing enumerable properties since the checks (in `src/core/worker.js`) done for `Array.prototype` *indirectly* also cover `Object`s. (Keep in mind that an `Array` is just a special kind of `Object` in JavaScript.)
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