The subnets which join to make the current subnet.

        In the case that self contains only one IP
        (self._prefixlen == 32 for IPv4 or self._prefixlen == 128
        for IPv6), yield an iterator with just ourself.

        Args:
            prefixlen_diff: An integer, the amount the prefix length
              should be increased by. This should not be set if
              new_prefix is also set.
            new_prefix: The desired new prefix length. This must be a
              larger number (smaller prefix) than the existing prefix.
              This should not be set if prefixlen_diff is also set.

        Returns:
            An iterator of IPv(4|6) objects.

        Raises:
            ValueError: The prefixlen_diff is too small or too large.
                OR
            prefixlen_diff and new_prefix are both set or new_prefix
              is a smaller number than the current prefix (smaller
              number means a larger network)

def subnets(self, prefixlen_diff=1, new_prefix=None):
        """The subnets which join to make the current subnet.

        In the case that self contains only one IP
        (self._prefixlen == 32 for IPv4 or self._prefixlen == 128
        for IPv6), yield an iterator with just ourself.

        Args:
            prefixlen_diff: An integer, the amount the prefix length
              should be increased by. This should not be set if
              new_prefix is also set.
            new_prefix: The desired new prefix length. This must be a
              larger number (smaller prefix) than the existing prefix.
              This should not be set if prefixlen_diff is also set.

        Returns:
            An iterator of IPv(4|6) objects.

        Raises:
            ValueError: The prefixlen_diff is too small or too large.
                OR
            prefixlen_diff and new_prefix are both set or new_prefix
              is a smaller number than the current prefix (smaller
              number means a larger network)

        """
        if self._prefixlen == self._max_prefixlen:
            yield self
            return

        if new_prefix is not None:
            if new_prefix < self._prefixlen:
                raise ValueError('new prefix must be longer')
            if prefixlen_diff != 1:
                raise ValueError('cannot set prefixlen_diff and new_prefix')
            prefixlen_diff = new_prefix - self._prefixlen

        if prefixlen_diff < 0:
            raise ValueError('prefix length diff must be > 0')
        new_prefixlen = self._prefixlen + prefixlen_diff

        if new_prefixlen > self._max_prefixlen:
            raise ValueError(
                'prefix length diff %d is invalid for netblock %s' % (
                    new_prefixlen, self))

        first = self.__class__('%s/%s' %
                                 (self.network_address,
                                  self._prefixlen + prefixlen_diff))

        yield first
        current = first
        while True:
            broadcast = current.broadcast_address
            if broadcast == self.broadcast_address:
                return
            new_addr = self._address_class(int(broadcast) + 1)
            current = self.__class__('%s/%s' % (new_addr,
                                                new_prefixlen))

            yield current