code: def _align_df(self, X: pd.DataFrame) -> pd.DataFrame:
      if self._feature_names is None:
          self._feature_names = list(X.columns)
      return X[self._feature_names]
  
imports: from __future__ import annotations
  import copy
  import functools
  import pandas
  from sklearn import base
  from sklearn import exceptions
  from river import base
label_desc: Use image node_id 3 for calling the SKL2RiverBase obj's underlying member method code with example usage: obj._align_df(X) and returns: X