docstr: Implement this method in a subclass to check
  if the model has been fit.
  
  Usually implements a model specific call to
  sklearn.utils.validation.check_is_fitted
  
  Returns
  -------
  bool
docstr_tok: ["Implement","this","method","in","a","subclass","to","check","if","the","model","has","been","fit",".","Usually","implements","a","model","specific","call","to","sklearn.utils.validation.check_is_fitted","Returns","--","--","--","-","bool"]
code: def _is_fitted(self):
      """
      Implement this method in a subclass to check
      if the model has been fit.
  
      Usually implements a model specific call to
      sklearn.utils.validation.check_is_fitted
  
      Returns
      -------
      bool
      """
      pass
  
imports: from abc import ABCMeta, abstractmethod
  from sklearn.exceptions import NotFittedError
  from sklearn.base import BaseEstimator
  import json
  import pickle
  import numpy
  from warnings import warn
label_desc: Use image node_id 1 for calling the BaseModelPackage obj's underlying member method code with example usage: obj._is_fitted() without return types