code: def _index_for_subslice(a: slice, sub: slice, length: int) -> slice:
      # Return slice c such that array[a][c] == array[sub].
      # sub should be contained in a.
      a_start, a_stop, a_step = a.indices(length)
      sub_start, sub_stop, sub_step = sub.indices(length)
  
      c_start = (sub_start - a_start) // a_step
      # a_start + a_step * (c_stop - 1) < sub_stop
      c_stop = (sub_stop - a_start - 1) // a_step + 1
      c_step = sub_step // a_step
  
      return slice(c_start, c_stop, c_step)
  
file_path: cupy/cupyx/distributed/array/_index_arith.py
imports: import typing
  from typing import Any, Optional
label_desc: Use image node_id 4 for calling a global function with example usage: _index_for_subslice(a, sub, length) and returns: slice