code: func NewTagIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *TagIter {
  	return &TagIter{iter, s}
  }
docs: // NewTagIter takes a storer.EncodedObjectStorer and a
  // storer.EncodedObjectIter and returns a *TagIter that iterates over all
  // tags contained in the storer.EncodedObjectIter.
  //
  // Any non-tag object returned by the storer.EncodedObjectIter is skipped.