Save the `bytes` under a key derived from `path` in Memcache.

        :return: A string representing the content path if it is stored.
        :rettype: string or None

def put(self, content_bytes):
        '''
        Save the `bytes` under a key derived from `path` in Memcache.

        :return: A string representing the content path if it is stored.
        :rettype: string or None
        '''
        derived_path = self.context.request.url
        over_max, content_size = self.content_size_exceeded_max(content_bytes)

        logger.debug('[{log_prefix}] content size in bytes: {size}'
            ' | is over max? {over_max} | skip storage? {skip}'.format(
            log_prefix=LOG_PREFIX, size=content_size, over_max=over_max,
            skip=self.skip_storage()))

        if (over_max and self.skip_storage()):
            # Short-circuit the storage when configured to skip large items
            logger.debug('[{log_prefix}] skipping storage: {content_size} '
                           'exceeds item_size_max of {max_size}'.format(
                           log_prefix=LOG_PREFIX, content_size=content_size,
                           max_size=self.item_size_max()))
            return None

        self.storage.set(
            self.timestamp_key_for(derived_path), datetime.utcnow(),
            time=self.context.config.RESULT_STORAGE_EXPIRATION_SECONDS
        )
        self.storage.set(
            self.result_key_for(derived_path), content_bytes,
            time=self.context.config.RESULT_STORAGE_EXPIRATION_SECONDS
        )

        return derived_path