This function was mistakenly typed as `Callable[[Property], object] |
None`, however the actual function accepts two parameters of type
`Property, value`. The value can be of any type. Strictly speaking, the
type corresponds to the type of the property which is defined at runtime.
Fixes#7103
The types for these class methods were mixed up. The async method
returned an optional `Model`, while the synchronous method returned a
`Future`. It's the other way around.
Fixes#7103
