'To get a range of data for group ID=[1, 2, 3]:
Returns a mapping of key => [(timestamp, count), ...].
>>> now = timezone.now()
>>> get_range([TSDBModel.group], [1, 2, 3],
>>>           start=now - timedelta(days=1),
>>>           end=now)'

def get_range(self, model, keys, start, end, rollup=None):

    raise NotImplementedError
