/**
  * {@inheritdoc}
  */
 public function flushAll()
 {
     $this->storage->doDelete($this->storageId);
     $this->content = array();
     $this->isDirty = false;
     return true;
 }
 /**
  * {@inheritdoc}
  */
 public function delete($id)
 {
     return $this->backend->doDelete($id);
 }