  For instance...

  ::

    >>> expand_ipv6_address('2001:db8::ff00:42:8329')
    '2001:0db8:0000:0000:0000:ff00:0042:8329'

    >>> expand_ipv6_address('::')
    '0000:0000:0000:0000:0000:0000:0000:0000'

    >>> expand_ipv6_address('::ffff:172.16.31.10')