Update and return model

Is your feature request related to a problem? Please describe.
I'm not sure if there's already a way to deal with it, but I couldn't find anything, so in case the functionality is implemented, it is not in the docs (or it's difficult to find it).

Describe the solution you'd like
In my case I'm using fastapi to update a model, call it myModel, which has M2M relations. In particular, I need to update the values of the fields in myModel and the M2M relations. I would like to update the fields and get the newly updated object, on which I can remove/add the M2M relations.

Describe alternatives you've considered
await myModel.get(id=id).update(
**input.dict(exclude_unset=True)
)
model = await myModel.get(id=id).prefetch_related("other_relation", "another_relation")
[model.other_relation.remove(x) for x in model.other_relations]
for id in other_rel_ids:
await model.other_relation.add(Other_relation.get(id=id))

# Similarly, for "another_relation"

In this case I need to execute the update query, then get the model and only then start updating the M2M relations. When tables are small it does not influence much performances, but for bigger tables it becomes a problem. Is there a way to update and get the model with the updated fields at once?

Additional context
Python: 3.8.5
Tortoise-orm: 0.16.20

No files or tests are named. Start by reviewing the existing Tortoise ORM update API and related documentation, then trace how model updates and many-to-many relations are handled. Done means the supported workflow can update fields, return the updated model, and allow subsequent many-to-many changes without the extra fetch described.