code: 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