code: protected function validateValue($value)
      {
          if ($this->strict) {
              $valid = $value === $this->trueValue || $value === $this->falseValue;
          } else {
              $valid = $value == $this->trueValue || $value == $this->falseValue;
          }
  
          if (!$valid) {
              return [$this->message, [
                  'true' => $this->trueValue === true ? 'true' : $this->trueValue,
                  'false' => $this->falseValue === false ? 'false' : $this->falseValue,
              ]];
          }
  
          return null;
      }
docs: {@inheritdoc}