how do you understand that python uses for in to subscribe to messages?

I used to work on the front end, and event subscriptions are written in this way, which is easy to understand.

eventBus.on("close", function(e){
 console.log(e)
})

recently, I learned that python, uses redis and kafka to do some message queuing, and I feel that I can"t understand the subscription of messages. I always thought that for in is just for looping, such as traversing items in any sequence, such as lists, tuples, and so on. so I can"t understand how python for in can listen for messages

after Google, I didn"t find the relevant explanation, only saw the relevant usage. It seems that no one is confused about this usage. I hope those who understand can explain it. Thank you.

// redis
import redis
...
for msg in sub.listen():
    print(msg)

// kafka
from kafka import KafkaConsumer
...
for message in consumer:
    print(message)