def ack!
      #:doc:
      logger.debug "Beetle: ack! for message #{msg_id}"
      header.ack
      return if simple? # simple messages don't use the deduplication store
      if !redundant? || @store.incr(msg_id, :ack_count) == 2
        @store.del_keys(msg_id)
      end
    end
def ack!
      #:doc:
      logger.debug "Beetle: ack! for message #{msg_id}"
      header.ack
      return if simple? # simple messages don't use the deduplication store
      if !redundant? || @store.incr(msg_id, :ack_count) == 2
        @store.del_keys(msg_id)
      end
    end
ack the message for rabbit. deletes all keys associated with this message in the
 deduplication store if we are sure this is the last message with the given msg_id.