code: def _fit(self, x: torch.Tensor) -> torch.Tensor:
      raise NotImplementedError
  
imports: from typing import Optional, Callable
  import torch
  from alibi_detect.od.pytorch.base import TorchOutlierDetector
  from alibi_detect.utils._types import TorchDeviceType
label_desc: Use image node_id 5 for calling the PCATorch obj's underlying member method code with example usage: obj._fit(x) without return types