Handle storage _adapter configuration
        :param app: Flask application

def _handle_adapter(self, app):
        """
        Handle storage _adapter configuration
        :param app: Flask application
        """
        if 'IMAGINE_ADAPTER' in app.config \
                and 'name' in app.config['IMAGINE_ADAPTER'] \
                and app.config['IMAGINE_ADAPTER']['name'] in self._adapters.keys():
            self._adapter = self._adapters[app.config['IMAGINE_ADAPTER']['name']](
                **app.config['IMAGINE_ADAPTER']
            )
        else:
            raise ValueError('Unknown _adapter: %s' % str(app.config['IMAGINE_ADAPTER']))