the problem here is that after deleting a given Hive we might end up with Session entities with no Hive and no Feeder attached. The usual solution to this would be to cascade delete  the Sessions - but if we do that we might also delete some Honeybees.
Before doing the actual Hive delete you need to do something like this (pseudo code):
``` python
for s in to_delete.sessions:
    if s it not a honeybee:
        db_session.delete(s)
```
The above code will force SQLalchemy to load and iterate each and every session attached to the Hive entity - feel free to come up with something wiser :)