@abc.abstractmethod<EOL><INDENT>def get_comment_form_for_update(self, comment_id):<DEDENT>
return<EOL>
Gets the comment form for updating an existing comment.

        A new comment form should be requested for each update
        transaction.

        :param comment_id: the ``Id`` of the ``Comment``
        :type comment_id: ``osid.id.Id``
        :return: the comment form
        :rtype: ``osid.commenting.CommentForm``
        :raise: ``NotFound`` -- ``comment_id`` is not found
        :raise: ``NullArgument`` -- ``comment_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*