[Outreachy] Blocked on Fedmsg app Beginner tasks

[Akanksha Nayak]

I am working on fedmsg app to trigger an event(source:
https://pagure.io/fedmsg-perceval-plugin)

Write a minimal fedmsg app which can trigger an event (can be anything like
tweeting, sending an IRC message, or anything crazy {Remember, sky is the
limit!}) using fedmsg.

I am referring to Ralph Bean's tutorials, here are some of the problems I
am facing understanding this

1. http://threebean.org/presentations/fedmsg-flock14/#/step-29
*topic_filter = 'fedoratagger' *-> who is publishing these topics on my
local system ?

2. Author is building an app to tweet and nowhere is he using the api

fedmsg.publish(source:http://www.fedmsg.com/en/stable/)

Instead he is using fedmsg.meta, fedmsg.config. There is no video recording
or context to understand why he is doing so, any pointers are welcome

3. Fedmsg is part of a pub-sub infrastructure, so when I am
developing/testing where are the endpoints that it is publishing to. It is
not very clear from the documentation.

Any links to tutorials, code or docs that can help me understand this
better is appreciated.

-Akanksha