code: def add_review_comment(self, doc, comment):
          
          if len(doc.reviews) != 0:
              if not self.review_comment_set:
                  self.review_comment_set = True
                  doc.reviews[-1].comment = comment
                  return True
              else:
                  raise CardinalityError('ReviewComment')
          else:
              raise OrderError('ReviewComment')
docs: Sets the review comment. Raises CardinalityError if
          already set. OrderError if no reviewer defined before.