code: def get_fetcher_assets(self, dt):
          
          # return a list of assets for the current date, as defined by the
          # fetcher source
          if self._extra_source_df is None:
              return []
  
          day = normalize_date(dt)
  
          if day in self._extra_source_df.index:
              assets = self._extra_source_df.loc[day]['sid']
          else:
              return []
  
          if isinstance(assets, pd.Series):
              return [x for x in assets if isinstance(x, Asset)]
          else:
              return [assets] if isinstance(assets, Asset) else []
docs: Returns a list of assets for the current date, as defined by the
          fetcher data.
  
          Returns
          -------
          list: a list of Asset objects.