How to use processors in filebeat HAproxy's module?

Sorry but my english is not good enough, which document is incorrect? I'm not trying to do very complicated stuff in processor, now I'm trying adding a tag, the final goal is to add a field only if the source.ip field is in a certain network CIDR. To do so I'll use the network condition and I know that I will need to upgrade to (at least) 7.2. Anyway, at the moment I'm only trying to make the processor working in the haproxy module.