def _normalize_timestamps(self, timestamp, intervals, config):
    '''
    Helper for the subclasses to generate a list of timestamps.
    '''
    rval = [timestamp]
    if intervals<0:
      while intervals<0:
        rval.append( config['i_calc'].normalize(timestamp, intervals) )
        intervals += 1
    elif intervals>0:
      while intervals>0:
        rval.append( config['i_calc'].normalize(timestamp, intervals) )
        intervals -= 1
    return rval
Helper for the subclasses to generate a list of timestamps.