Log the planned IP address changes.

    Args:
      configured: list, the IP address strings already configured.
      desired: list, the IP address strings that will be configured.
      to_add: list, the forwarded IP address strings to configure.
      to_remove: list, the forwarded IP address strings to delete.
      interface: string, the output device to modify.

def _LogForwardedIpChanges(
      self, configured, desired, to_add, to_remove, interface):
    """Log the planned IP address changes.

    Args:
      configured: list, the IP address strings already configured.
      desired: list, the IP address strings that will be configured.
      to_add: list, the forwarded IP address strings to configure.
      to_remove: list, the forwarded IP address strings to delete.
      interface: string, the output device to modify.
    """
    if not to_add and not to_remove:
      return
    self.logger.info(
        'Changing %s IPs from %s to %s by adding %s and removing %s.',
        interface, configured or None, desired or None, to_add or None,
        to_remove or None)