* rename get_data_size.
* remove g from DistTensor.
* remove g from DistEmbedding.
* clean up API of graph partition book.
* fix DistGraph
* fix lint.
* collect all part policies.
* fix.
* fix.
* support distributed sampler.
* remove partition.py
* add standalone mode
* add comments.
* add tests for sampling.
* fix.
* make the code to run the standalone mode
* fix
* fix
* fix readme.
* fix.
* fix test
Co-authored-by: Chao Ma <mctt90@gmail.com>