def get_boundaries(self, filter_type, value):
        assert filter_type in self.handled_suffixes
        start = '-'
        end = '+'
        exclude = None
        if filter_type in (None, 'eq'):
            start = u'[%s%s' % (value, self.separator)
            end = start.encode('utf-8') + b'\xff'
        elif filter_type == 'gt':
            start = u'(%s' % value
            exclude = value
        elif filter_type == 'gte':
            start = u'[%s' % value
        elif filter_type == 'lt':
            end = u'(%s' % value
            exclude = value
        elif filter_type == 'lte':
            end = u'[%s%s' % (value, self.separator)
            end = end.encode('utf-8') + b'\xff'
        elif filter_type == 'startswith':
            start = u'[%s' % value
            end = start.encode('utf-8') + b'\xff'
        return start, end, exclude