code: def _get_napp_key(self, key, user=None, napp=None):
          
          if user is None:
              user = self.user
          if napp is None:
              napp = self.napp
          kytos_json = self._installed / user / napp / 'kytos.json'
          try:
              with kytos_json.open() as file_descriptor:
                  meta = json.load(file_descriptor)
                  return meta[key]
          except (FileNotFoundError, json.JSONDecodeError, KeyError):
              return ''
docs: Return a value from kytos.json.
  
          Args:
              user (string): A Username.
              napp (string): A NApp name
              key (string): Key used to get the value within kytos.json.
  
          Returns:
              meta (object): Value stored in kytos.json.