code: def subtract_mean(x: torch.Tensor) -> torch.Tensor:
      mean = [0.406, 0.456, 0.485]
      x[:, 0, :, :] -= mean[0]
      x[:, 1, :, :] -= mean[1]
      x[:, 2, :, :] -= mean[2]
      return x
  
imports: from __future__ import annotations
  import warnings
  import torch
  import torch.nn
  from monai.utils import optional_import
  from monai.utils.enums import StrEnum
label_desc: Use image node_id 6 for calling a global function with example usage: subtract_mean(x) and returns: x