code: def set_journal_comment(self, comment):
          
          self._my_map['journal_comment'] = self._get_display_text(comment, self.get_journal_comment_metadata())
docs: Sets a comment.
  
          arg:    comment (string): the new comment
          raise:  InvalidArgument - ``comment`` is invalid
          raise:  NoAccess - ``Metadata.isReadonly()`` is ``true``
          raise:  NullArgument - ``comment`` is ``null``
          *compliance: mandatory -- This method must be implemented.*