docs: def get_bars(self, lookback=None, as_dict=False):
          """ Get bars for this instrument
  
          :Parameters:
              lookback : int
                  Max number of bars to get (None = all available bars)
              as_dict : bool
                  Return a dict or a pd.DataFrame object
  
          :Retruns:
              bars : pd.DataFrame / dict
                  The bars for this instruments
          """
          bars = self._get_symbol_dataframe(self.parent.bars, self)
  
          # add signal history to bars
          bars = self.parent._add_signal_history(df=bars, symbol=self)
  
          lookback = self.bar_window if lookback is None else lookback
          bars = bars[-lookback:]
          # if lookback is not None:
          #     bars = bars[-lookback:]
  
          if not bars.empty > 0 and bars['asset_class'].values[-1] not in ("OPT", "FOP"):
              bars.drop(bars.columns[
                  bars.columns.str.startswith('opt_')].tolist(),
                  inplace=True, axis=1)
  
          if as_dict:
              bars.loc[:, 'datetime'] = bars.index
              bars = bars.to_dict(orient='records')
              if lookback == 1:
                  bars = None if not bars else bars[0]
  
          return bars