code: def create_index(group, chunk_size, compression=None, compression_opts=None):
      
      dtype = np.int64
      if chunk_size == 'auto':
          chunks = True
      else:
          chunks = (nb_per_chunk(np.dtype(dtype).itemsize, 1, chunk_size),)
  
      group.create_dataset(
          'index', (0,), dtype=dtype,
          chunks=chunks, maxshape=(None,),
          compression=compression, compression_opts=compression_opts)
docs: Create an empty index dataset in the given group.