code: def req2frame(req, N: int=0):
      
      if req is None:
          frame = np.arange(N, dtype=np.int64)
      elif isinstance(req, int):  # the user is specifying a step size
          frame = np.arange(0, N, req, dtype=np.int64)
      elif len(req) == 1:
          frame = np.arange(0, N, req[0], dtype=np.int64)
      elif len(req) == 2:
          frame = np.arange(req[0], req[1], dtype=np.int64)
      elif len(req) == 3:
          # this is -1 because user is specifying one-based index
          frame = np.arange(req[0], req[1], req[2],
                            dtype=np.int64) - 1  # keep -1 !
      else:  # just return all frames
          frame = np.arange(N, dtype=np.int64)
  
      return frame
docs: output has to be numpy.arange for > comparison