code: def _shifted_cumprod(x, shift: int = 1):
      """
      Computes `torch.cumprod(x, dim=-1)` and prepends `shift` number of
      ones and removes `shift` trailing elements to/from the last dimension
      of the result.
      """
      x_cumprod = torch.cumprod(x, dim=-1)
      x_cumprod_shift = torch.cat(
          [
              torch.ones_like(x_cumprod[..., :shift]),
              x_cumprod[..., :-shift],
          ],
          dim=-1,
      )
      return x_cumprod_shift
  
file_path: pytorch3d/pytorch3d/renderer/implicit/raymarching.py
imports: import warnings
  from typing import Optional, Tuple, Union
  import torch
label_desc: Use image node_id 1 for calling a global function with example usage: _shifted_cumprod(x, shift) and returns: x_cumprod_shift