docstr: Raises error if parent object instance has not been fit.
docstr_tok: ["Raises","error","if","parent","object","instance","has","not","been","fit","."]
code: def _check_fitted(self):
      """Raises error if parent object instance has not been fit."""
      if not self.fitted:
          raise NotFittedError(self.__class__.__name__)
  
imports: from abc import ABC, abstractmethod
  from typing import Optional
  from typing_extensions import Self
  import torch
  import numpy
  from torch.nn import Module
  from alibi_detect.exceptions import NotFittedError
label_desc: Use image node_id 4 for calling the FitMixinTorch obj's underlying member method code with example usage: obj._check_fitted() without return types