class_docstr: Shared set-up checks and methods across selectors.
  
  Parameters
  ----------
  confirm_variables: bool, default=False
      If set to True, variables that are not present in the input dataframe will be
      removed from the indicated list of variables. See parameter variables for more
      details.
  
  Methods
  -------
  transform:
      Remove non-selected features.
  
  _confirm_variables:
      Check that the variables entered by the user exist in the df.
class_docstr_tok: ["Shared","set-up","checks","and","methods","across","selectors",".","Parameters","--","--","--","--","--","confirm_variables",":","bool",",","default=False","If","set","to","True",",","variables","that","are","not","present","in","the","input","dataframe","will","be","removed","from","the","indicated","list","of","variables",".","See","parameter","variables","for","more","details",".","Methods","--","--","--","-","transform",":","Remove","non-selected","features",".","_confirm_variables",":","Check","that","the","variables","entered","by","the","user","exist","in","the","df","."]
code: def _confirm_variables(self, X: pd.DataFrame) -> None:
      # If required, exclude variables that are not in the input dataframe
      if self.confirm_variables:
          self.variables_ = _filter_out_variables_not_in_dataframe(
              X, self.variables
          )
      else:
          self.variables_ = self.variables
  
      return None
  
imports: import numpy
  import pandas
  from sklearn.base import BaseEstimator, TransformerMixin
  from sklearn.utils.validation import check_is_fitted
  from feature_engine._base_transformers.mixins import GetFeatureNamesOutMixin
  from feature_engine._variable_handling.variable_type_selection import _filter_out_variables_not_in_dataframe
  from feature_engine.dataframe_checks import _check_X_matches_training_df, check_X
  from feature_engine.tags import _return_tags
label_desc: Use image node_id 4 for calling the BaseSelector obj's underlying member method code with example usage: obj._confirm_variables(X) and returns: None