The origin of the error is traced to line 56. Here it is:

sqlalchemy.exc.ProgrammingError: (sqlite3.ProgrammingError) SQLite objects created in a thread can only be used in that
same thread. The object was created in thread id 8628 and this is thread id 5372.
[SQL: SELECT puppy.name AS puppy_name, puppy.id AS puppy_id, puppy.description AS puppy_description
FROM puppy]
[parameters: [immutabledict({})]]

As a newbie, I find this quite cryptic and am unable to completely deduce what caused this.

Thanks,
Reece