Turn the prefix length netmask into a int for comparison.

        Args:
            prefixlen: An integer, the prefix length.

        Returns:
            An integer.

def _ip_int_from_prefix(self, prefixlen=None):
        """Turn the prefix length netmask into a int for comparison.

        Args:
            prefixlen: An integer, the prefix length.

        Returns:
            An integer.

        """
        if prefixlen is None:
            prefixlen = self._prefixlen
        return self._ALL_ONES ^ (self._ALL_ONES >> prefixlen)