Annotation for configuration values

[bpiwowar]

Allows to declare easily an external value class, which is useful to avoid initialising resources (e.g. torch) when not needed

class Model(Config):
   ...

@Model.value
class TorchModel(Model, nn.Module):
   ...

class SubModel(Model):
   ...

@SubModel.value
class TorchSubModel(SubModel, TorchModel):
  "We need to inherit from both the configuration `SubModel` and the `Model` value, i.e. `TorchModel`"
   ...

• Create the tests
• Implement the value class method which should test whether the value classes (1) is a subclass of the configuration, (2) is a subclass of the parent configuration values (if any)
• Check that if A has a value class AValue, SubA has none, and SubSubA has, then the latter inherits from SubA.XPMValue and that SubA.XPMValue implicitely inherits drom AValue