code: def fit(self, data):
          
          if not self._transformers:
              return
  
          transformed_data = self._preprocess(data)
          final_step = self._transformers[-1]
          final_step[1].fit(transformed_data)
docs: Fits a transformer using the SFrame `data`.
  
          Parameters
          ----------
          data : SFrame
              The data used to fit the transformer.
  
          Returns
          -------
          self (A fitted object)
  
          See Also
          --------
          transform, fit_transform
  
          Examples
          --------
          .. sourcecode:: python
  
            >> chain = chain.fit(sf)