class Redis

def _subscription(method, timeout, channels, block)
  if block
    if @subscription_client
      raise SubscriptionError, "This client is already subscribed"
    end
    begin
      @subscription_client = SubscribedClient.new(@client.pubsub)
      if timeout > 0
        @subscription_client.send(method, timeout, *channels, &block)
      else
        @subscription_client.send(method, *channels, &block)
      end
    ensure
      @subscription_client = nil
    end
  else
    unless @subscription_client
      raise SubscriptionError, "This client is not subscribed"
    end
    @subscription_client.call_v([method].concat(channels))
  end
end