code: def change_hosts(self, mode, host_family, host, onerror = None):
          
          request.ChangeHosts(display = self.display,
                              onerror = onerror,
                              mode = mode,
                              host_family = host_family,
                              host = host)
docs: mode is either X.HostInsert or X.HostDelete. host_family is
          one of X.FamilyInternet, X.FamilyDECnet or X.FamilyChaos.
  
          host is a list of bytes. For the Internet family, it should be the
          four bytes of an IPv4 address.