code: def get_pool_for_host(self, host_id):
          
          if isinstance(host_id, HostInfo):
              host_info = host_id
              host_id = host_info.host_id
          else:
              host_info = self.hosts.get(host_id)
              if host_info is None:
                  raise LookupError('Host %r does not exist' % (host_id,))
  
          rv = self._pools.get(host_id)
          if rv is not None:
              return rv
          with self._lock:
              rv = self._pools.get(host_id)
              if rv is None:
                  opts = dict(self.pool_options or ())
                  opts['db'] = host_info.db
                  opts['password'] = host_info.password
                  if host_info.unix_socket_path is not None:
                      opts['path'] = host_info.unix_socket_path
                      opts['connection_class'] = UnixDomainSocketConnection
                      if host_info.ssl:
                          raise TypeError('SSL is not supported for unix '
                                          'domain sockets.')
                  else:
                      opts['host'] = host_info.host
                      opts['port'] = host_info.port
                      if host_info.ssl:
                          if SSLConnection is None:
                              raise TypeError('This version of py-redis does '
                                              'not support SSL connections.')
                          opts['connection_class'] = SSLConnection
                          opts.update(('ssl_' + k, v) for k, v in
                                      (host_info.ssl_options or {}).iteritems())
                  rv = self.pool_cls(**opts)
                  self._pools[host_id] = rv
              return rv
docs: Returns the connection pool for the given host.
  
          This connection pool is used by the redis clients to make sure
          that it does not have to reconnect constantly.  If you want to use
          a custom redis client you can pass this in as connection pool
          manually.