code: func (s *symbol) HasDocTag(tag string) bool {
  	if s.tags == nil {
  		s.tags = stringset.Set{}
  		for _, word := range strings.Fields(s.Doc().RemarkBlock("DocTags").Body) {
  			s.tags.Add(strings.ToLower(strings.Trim(word, ".,")))
  		}
  	}
  	return s.tags.Has(strings.ToLower(tag))
  }
docs: // HasDocTag returns true if the docstring has a section "DocTags" and the
  // given tag is listed there.
  //
  // Used to mark some symbols as advanced, or experimental.