code: def _get_paging_controls(request):
          
          start = request.url.query.get('start', None)
          limit = request.url.query.get('limit', None)
          controls = {}
  
          if limit is not None:
              try:
                  controls['limit'] = int(limit)
              except ValueError:
                  LOGGER.debug('Request query had an invalid limit: %s', limit)
                  raise errors.CountInvalid()
  
              if controls['limit'] <= 0:
                  LOGGER.debug('Request query had an invalid limit: %s', limit)
                  raise errors.CountInvalid()
  
          if start is not None:
              controls['start'] = start
  
          return controls
docs: Parses start and/or limit queries into a paging controls dict.