def _prefix_from_ip_int(self, ip_int, mask=<NUM_LIT:32>):
return mask - _count_righthand_zero_bits(ip_int, mask)<EOL>
Return prefix length from the decimal netmask.

        Args:
            ip_int: An integer, the IP address.
            mask: The netmask.  Defaults to 32.

        Returns:
            An integer, the prefix length.