code: def consume
        unless consumer_channels
          @consumer_channels ||= consumer_connections.map do |conn|
            open_channel(conn, config.prefetch)
          end
  
          subscriptions.each { |args| subscribe(*args) }
        end
  
        self
      end
docs: Opens connections, channels, and sets up and specified subscriptions
   invoking {Messaging::Consumer#on_message} when a payload is received.
  
   Evaluation: Eager - This is only required to evaluate and declare the
   subscriptions which have been deffered using class .subscribe
  
   @return [Messaging::Consumer]
   @api public