Properties that compute their value: [smartproperty][brainhops._core.properties.smartproperty] and
[lazyproperty][brainhops._core.properties.lazyproperty] (computed on first access, then cached).
Attributes
UnsetLikemodule-attribute
UnsetLike=_UnsetForm|tuple[_UnsetForm,...]
When a stored value reads as unset: None, "empty", a predicate, or
a tuple of them (see [smartproperty][brainhops._core.properties.smartproperty]).