code: public function has(string $key) : bool
      {
          $parts = explode('.', $key);
  
          $current = $this->data;
  
          while (count($parts) > 0) {
              $part = array_shift($parts);
  
              if (false === isset($current[$part])) {
                  return false;
              }
  
              $current = $current[$part];
          }
  
          return true;
      }
docs: @inheritdoc
  
  @param string $key
  
  @return bool