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Triggers are useful for a wide range of cases, like verifying constraints or boosting performance. In our case, we will use triggers to notify our Python listener when data has been removed or added. We define a procedure called `notify_account_changes()` that will handle sending notifications about the changes in the database. We can have many listeners on a channel by executing `LISTEN channel_name. And to send notifications, we use the `NOTIFY` command or the built-in system function `pg_notify('channel_name', 'payload')