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