Hub.Channel.unsubscribe_and_flush

You're seeing just the function unsubscribe_and_flush, go back to Hub.Channel module for more information.
Link to this function

unsubscribe_and_flush(subscription_ref)

Specs

unsubscribe_and_flush(subscription_ref()) :: :ok

Unsubscribes and flushes any messages in the mailbox that matches the subscribed pattern