class_docstr: Abstract base class for preprocessing defences.
  
  By default, the gradient is estimated using BPDA with the identity function.
      To modify, override `estimate_gradient`
docstr: Return the state of the preprocessing object.
  
  :return: `True` if the preprocessing model has been fitted (if this applies).
docstr_tok: ["Return","the","state","of","the","preprocessing","object",".",":","return",":","`","True","`","if","the","preprocessing","model","has","been","fitted","(","if","this","applies",")","."]
code: def is_fitted(self) -> bool:
      """
      Return the state of the preprocessing object.
  
      :return: `True` if the preprocessing model has been fitted (if this applies).
      """
      return self._is_fitted
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import abc
  from typing import List, Optional, Tuple, Any, TYPE_CHECKING
  import numpy
  from art import config
label_desc: Use image node_id 2 for calling the Preprocessor obj's underlying member method code with example usage: obj.is_fitted() and returns: self