code: public function create($key, $value)
      {
          $exists = $this->metaModel::where('key', $key)
              ->exists();
  
          if ($exists) {
              $message = "Can't create meta (key: $key). ";
              $message .= "Meta already exists";
              throw new \Exception($message);
          }
  
          $meta = new $this->metaModel;
  
          $meta->key = $key;
          $meta->value = $value;
  
          $meta->save();
      }
docs: Create meta at given key
  for package realm.
  If meta exists, exception will be thrown.
  
  @param string $key
  @param mixed  $value
  
  @throws \Exception