Connect to the following signals to get notified before and after
changes are committed to the database. Tracking changes adds significant
overhead, so it is only enabled if
enabled in the config. In most cases, you’ll probably be better served
by using SQLAlchemy events directly.
This signal is sent when changed models are committed to the database.
The sender is the application that emitted the changes. The receiver is passed the
changesparameter with a list of tuples in the form
(model instance, operation).
The operation is one of