BSA — inheritance in annotation iterators

During BSA implementation we have found that SeqAnnotationIterator does
not inherit from AnnotationIterator, and that SeqAnnotationIterator is
not used explicitly anywhere in the spec. Please can you remind me why it
is like that, or confirm my feeling that something is missing there?

I see several possible solutions of this issue - ca we discuss them
briefly before going to the "resolution?

1) Nothing is wrong in current spec, I have just missed something.

2) The SeqAnnotationIterator will inherit from AnnotationIterator and its
next() and next_n() methods will be renamed to something
like next_seq_anno() and next_n_seq_anno(). Obviously, there would have be
explanation that methods next() and next_seq_anno() should behave the
same. Not too nice, and not too OO.

3) The SeqAnnotationIterator will inherit from AnnotationIterator but will
remain empty. Does this bring "more type safety" - that is the claimed
reason why we have SeqAnnotationIterator at the first place.

4) The SeqAnnotationIterator will be removed completely.

5) BioSequence interface will get an addition method get_seq_annotations
returning in out parameter a SeqAnnotationIterator (no inheritance between
iterators needed).

To be honest I cannot make my mind which solution I would prefer at the
moment. Probably the ad 1).

accepted