code: def fit(self, X):
          
          if isinstance(X, (pd.Series, pd.DataFrame)):
              self.name = X.name
  
          self.constant_value = self._get_constant_value(X)
  
          if self.constant_value is None:
              self.mean = np.mean(X)
              self.std = np.std(X)
  
          else:
              self._replace_constant_methods()
  
          self.fitted = True
docs: Fit the model.
  
          Arguments:
              X: `np.ndarray` of shape (n, 1).
  
          Returns:
              None