SourcePackageSet claims to implement ISourcePackageSet, but doesn't

Looking at the SourcePackageSet, one sees:

  class SourcePackageSet(object):
      """A set of Magic SourcePackage objects."""

      implements(ISourcePackageSet)
      ...

However, this is untrue; SourcePackageSet is missing several methods documented in the ISourcePackageSet interface, e.g. findByNameInDistroRelease, getByNameInDistroRelease, getSourcePackageRelease, etc.

Either the interface needs to be fixed, the implementation needs to be fixed, or both the interface and the implementation need to be fixed.