Delete all keys from the relation for the specified source.
Must be called within a Relation.change callback.
NOTE: TypeScript's structural typing allows readonly objects to be passed to Mutable<T>
parameters, so there is no compile-time error. Enforcement is runtime-only.
Delete all keys from the relation for the specified source. Must be called within a
Relation.changecallback.NOTE: TypeScript's structural typing allows readonly objects to be passed to
Mutable<T>parameters, so there is no compile-time error. Enforcement is runtime-only.