úÎí—Safe9;kA class of types that have additional invariants defined upon them that aren't enforced by the type systemAny FoldableH of things that can be checked for validity can be checked for validity»This includes lists, which means that the empty list is considered valid. If the empty list should not be considered valid as part of your custom data type, make sure to write a custom Validity instanceThis also includes Maybe!: It makes sense to assume that Z is valid. If Nothing wasn't valid, you wouldn't have used a Maybe in the datastructure.Safe9;<=kA class of types that have additional invariants defined upon them that aren't enforced by the type systemIf there is a  Validity a instance as well, then a  b should imply  isValid a for any b.If there is a  Validity b instance as well, then a  b should imply  isValid b for any a.  &validity-0.2.0.0-L9ZHvCFGQ8918Ty0ryquy Data.ValidityData.RelativeValidityValidityisValid $fValiditytRelativeValidity isValidForbaseGHC.BaseNothing