code: def add_annotation_comment(self, doc, comment):
          
          if len(doc.annotations) != 0:
              if not self.annotation_comment_set:
                  self.annotation_comment_set = True
                  doc.annotations[-1].comment = comment
                  return True
              else:
                  raise CardinalityError('AnnotationComment')
          else:
              raise OrderError('AnnotationComment')
docs: Sets the annotation comment. Raises CardinalityError if
          already set. OrderError if no annotator defined before.