OptionalconditionalClasses listed by exportClasses(): the S4 classes the package owns. Separated like exportedS4Methods.
Names listed by exportMethods(): S4 methods the package registered for one of its classes, which is a
different claim than an ordinary export (the package answers a generic, it does not define the function).
As R's loadNamespace, this keeps only the non-primitive generics: a method on a primitive such as + or [
binds nothing in the namespace, so pkg::"+" does not exist and the call stays with base.
Optionals3For S3method(generic, class, fun), the function registered as the method generic.class when it is not named so.
Present only in complex parsed NAMESPACE files. Maps conditions to the parts they gate.