old_contents: from .core import (DataFrame, Series, Index, _Frame, concat, map_partitions,
          repartition)
  from .io import (read_csv, from_array, from_bcolz, from_array, from_bcolz,
                   from_pandas, from_dask_array, from_castra, read_hdf)
  from .optimize import optimize
  from .multi import merge
  from .rolling import (rolling_count, rolling_sum, rolling_mean, rolling_median,
                        rolling_min, rolling_max, rolling_std, rolling_var,
                        rolling_skew, rolling_kurt, rolling_quantile, rolling_apply,
                        rolling_window)
  from ..base import compute
  
new_contents: from .core import (DataFrame, Series, Index, _Frame, concat, map_partitions,
          repartition)
  from .io import (read_csv, from_array, from_bcolz, from_array, from_bcolz,
                   from_pandas, from_dask_array, from_castra, read_hdf)
  from .optimize import optimize
  from .multi import merge
  from .rolling import (rolling_count, rolling_sum, rolling_mean, rolling_median,
                        rolling_min, rolling_max, rolling_std, rolling_var,
                        rolling_skew, rolling_kurt, rolling_quantile, rolling_apply,
                        rolling_window)
  from ..base import compute
  from . import demo
  
subject: add demo to dataframe/__init__.py