code: def fit(
      self,
      X: pd.DataFrame,
      y_hat: pd.Series,
      y: pd.Series,
      s: Optional[pd.Series] = None,
  ) -> None:
      pass
  
file_path: aequitas/src/aequitas/fairflow/methods/postprocessing/identity.py
imports: from typing import Optional
  import pandas
  from .postprocessing import PostProcessing
label_desc: Use image node_id 2 for calling the Identity obj's underlying member method code with example usage: obj.fit(X, y_hat, y, s) without return types