docs: function Nullable (val) {
    if (!(this instanceof Nullable)) { return new Nullable(val) }
    if (val instanceof Nullable) { return val }
    this.value = val
    this.type = typeof val
    this.isNull = val === null
    this.isUndefined = val === void 0
    this.hasValue = !(this.isNull || this.isUndefined)
    Object.freeze(this)
  }