def filterAcceptsRow(self, row, parentindex):
        """Return True, if the filter accepts the given row of the parent

        :param row: the row to filter
        :type row: :class:`int`
        :param parentindex: the parent index
        :type parentindex: :class:`QtCore.QModelIndex`
        :returns: True, if the filter accepts the row
        :rtype: :class:`bool`
        :raises: None
        """
        if not super(ReftrackSortFilterModel, self).filterAcceptsRow(row, parentindex):
            return False
        if parentindex.isValid():
            m = parentindex.model()
        else:
            m = self.sourceModel()

        i = m.index(row, 18, parentindex)
        reftrack = i.data(REFTRACK_OBJECT_ROLE)
        if not reftrack:
            return True
        else:
            return self.filter_accept_reftrack(reftrack)