code: def epochrange(self, epoch=None, starttime=None, endtime=None):
          
          return self.varget(variable=epoch, starttime=starttime,
                             endtime=endtime, record_range_only=True)
docs: Get epoch range.
  
          Returns a list of the record numbers, representing the
          corresponding starting and ending records within the time
          range from the epoch data. A None is returned if there is no
          data either written or found in the time range.