docstr: positions = [B*N, 3]
docstr_tok: ["positions","=","[","B","*","N",",","3","]"]
code: def encode(self, rays_d: torch.Tensor) -> torch.Tensor:
      """
      positions = [B*N, 3]
      """
      raise NotImplementedError
  
imports: import torch
  import torch.nn
label_desc: Use image node_id 2 for calling the NeRFBackgroundBase obj's underlying member method code with example usage: obj.encode(rays_d) without return types