code: def get_ip6_address(interface_name, expand=False):
      
      address = _get_address(interface_name, IP6_PATTERN)
      if address and expand:
          return ':'.join(_expand_groups(address))
      return address
docs: Extracts the IPv6 address for a particular interface from `ifconfig`.
  
      :param interface_name: Name of the network interface (e.g. ``eth0``).
      :type interface_name: unicode
      :param expand: If set to ``True``, an abbreviated address is expanded to the full address.
      :type expand: bool
      :return: IPv6 address; ``None`` if the interface is present but no address could be extracted.
      :rtype: unicode