I've discovered if I use an object (found by session.query) as the value
for the relationship field, I get the issue of having objects being added
without explicit add() method.
But if I insert, for the relationship, the id of the register in database
(of the object got by session.query), I
You're experiencing exactly what Michael pointed you to.
Person has a relationship+backref to SourceDatabase though
`Person.source_database`. When you create a `John` and assign the existing
source_database, sqlalchemy is implicitly adding the Person so that the
update you explicitly
