metric aggregation error

  File "/usr/local/lib/python2.7/dist-packages/pecan/middleware/debug.py", line 74, in __call__
    return self.app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/pecan/middleware/recursive.py", line 56, in __call__
    return self.application(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/pecan/core.py", line 829, in __call__
    return super(Pecan, self).__call__(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/pecan/core.py", line 678, in __call__
    self.invoke_controller(controller, args, kwargs, state)
  File "/usr/local/lib/python2.7/dist-packages/pecan/core.py", line 572, in invoke_controller
    result = controller(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/gnocchi/rest/__init__.py", line 1292, in post
    metrics, start, stop, aggregation, needed_overlap)
  File "/usr/local/lib/python2.7/dist-packages/gnocchi/rest/__init__.py", line 416, in get_cross_metric_measures_from_objs
    metrics, start, stop, aggregation, needed_overlap)
  File "/usr/local/lib/python2.7/dist-packages/gnocchi/storage/_carbonara.py", line 252, in get_cross_metric_measures
    aggregation, needed_overlap)]
  File "/usr/local/lib/python2.7/dist-packages/gnocchi/carbonara.py", line 501, in aggregated
    points = (agg_timeserie.sort_values(by=['granularity', 'timestamp'],
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/generic.py", line 2150, in __getattr__
    (type(self).__name__, name))
AttributeError: 'DataFrame' object has no attribute 'sort_values'