code: func (fkvs *FileKeyValueStore) Load(key interface{}) (interface{}, error) {
  	file, err := fkvs.keySerializer(key)
  	if err != nil {
  		return nil, err
  	}
  	if _, err1 := os.Stat(file); os.IsNotExist(err1) {
  		return nil, core.ErrKeyValueNotFound
  	}
  	bytes, err := ioutil.ReadFile(file) // nolint: gas
  	if err != nil {
  		return nil, err
  	}
  	if bytes == nil {
  		return nil, core.ErrKeyValueNotFound
  	}
  	return fkvs.unmarshaller(bytes)
  }
docs: // Load returns the value stored in the store for a key.
  // If a value for the key was not found, returns (nil, ErrNotFound)