code: public function delete(Mapper $mapper, $object)
      {
          $map                = $mapper->getMap();
          $reflectionProperty = new \ReflectionProperty($map->getLocalName(), $map->getIdentifier());
          $reflectionProperty->setAccessible(true);
          $identifier = $reflectionProperty->getValue($object);
          $uri        = $this->buildUri($map->getRemoteName() . '/' . $identifier);
          if (!file_exists($uri)) {
              return true;
          }
          if ($this->context) {
              return unlink($uri, $this->context);
          }
          return unlink($uri);
      }
docs: @param Mapper $mapper
  @param mixed  $object
  
  @return bool