code: def _ParseTimeRange(self, timerange):
      
      if timerange is None:
        timerange = (None, None)
  
      from_time, to_time = timerange
      if not from_time:
        from_time = rdfvalue.RDFDatetime().FromSecondsSinceEpoch(0)
  
      if not to_time:
        to_time = rdfvalue.RDFDatetime().FromSecondsSinceEpoch(sys.maxsize)
  
      return (from_time, to_time)
docs: Parses a timerange argument and always returns non-None timerange.