Method is_bool

src/framework/io/json.cpp:199–201

Value::Value(const Value & other)
    : kind_(other.kind_),
      bool_value_(other.bool_value_),
      number_value_(other.number_value_),
      string_value_(other.string_value_) {
    if (other.array_value_) {
        array_value_ = std::make_unique<Array>(*other.array_value_);