code: def set_max_connections_per_host(self, host_distance, max_connections):
          
          if self.protocol_version >= 3:
              raise UnsupportedOperation(
                  "Cluster.set_max_connections_per_host() only has an effect "
                  "when using protocol_version 1 or 2.")
          self._max_connections_per_host[host_distance] = max_connections
docs: Sets the maximum number of connections per Session that will be opened
          for each host with :class:`~.HostDistance` equal to `host_distance`.
          The default is 2 for :attr:`~HostDistance.LOCAL` and 1 for
          :attr:`~HostDistance.REMOTE`.
  
          If :attr:`~.Cluster.protocol_version` is set to 3 or higher, this
          is not supported (there is always one connection per host, unless
          the host is remote and :attr:`connect_to_remote_hosts` is :const:`False`)
          and using this will result in an :exc:`~.UnsupporteOperation`.