@abc.abstractmethod<EOL><INDENT>def get_comments_for_reference(self, reference_id):<DEDENT>
return<EOL>
Gets a list of comments corresponding to a reference ``Id``.

        :param reference_id: the ``Id`` of the reference
        :type reference_id: ``osid.id.Id``
        :return: the returned ``CommentList``
        :rtype: ``osid.commenting.CommentList``
        :raise: ``NullArgument`` -- ``reference_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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