saveStateBeforeParse() {
    this._savedState = {
      // name is stable if supplied by author, but may be unspecified for root command and deduced during parsing
      _name: this._name,
      // option values before parse have default values (including false for negated options)
      // shallow clones
      _optionValues: { ...this._optionValues },
      _optionValueSources: { ...this._optionValueSources },
    };
  }
Called the first time parse is called to save state and allow a restore before subsequent calls to parse.
Not usually called directly, but available for subclasses to save their custom state.

This is called in a lazy way. Only commands used in parsing chain will have state saved.