Should we support a way to define default link's value?

Should it be an architectural change or it can be done as an optional package?

If it is optional package, than we can implement it as a decorator for DeepClient.

For example we can have a default value for a link as 0 or 10 or any other.
Then if we do not store value for that link, and default value is not empty if we try to load a value, using `value` relationship we will get that value even if for that link value was never specified after the creation.