def get_boundaries(self, filter_type, value):
        assert filter_type in self.handled_suffixes
        start = '-inf'
        end = '+inf'
        exclude = None
        if filter_type in (None, 'eq'):
            start = end = value
        elif filter_type == 'gt':
            start = '(%s' % value
        elif filter_type == 'gte':
            start = value
        elif filter_type == 'lt':
            end = '(%s' % value
        elif filter_type == 'lte':
            end = value
        return start, end, exclude