Check if a URL (and xpath) exists in the cache

        If DB has not been initialized yet, returns ``False`` for any URL.

        Args:
            url (str): If given, clear specific item only. Otherwise remove the DB file.
            xpath (str): xpath to search (may be ``None``)

        Returns:
            bool: ``True`` if URL exists, ``False`` otherwise

def has(self, url, xpath=None):
        """Check if a URL (and xpath) exists in the cache

        If DB has not been initialized yet, returns ``False`` for any URL.

        Args:
            url (str): If given, clear specific item only. Otherwise remove the DB file.
            xpath (str): xpath to search (may be ``None``)

        Returns:
            bool: ``True`` if URL exists, ``False`` otherwise
        """
        if not path.exists(self.db_path):
            return False

        return self._query(url, xpath).count() > 0