code: def _register_order_book_channels(self):
          
          channels = {'order_book': self.btcusd_ob_callback,
                      'order_book_btceur': self.btceur_ob_callback,
                      'order_book_eurusd': self.eurusd_ob_callback,
                      'order_book_xrpusd': self.xrpusd_ob_callback,
                      'order_book_xrpeur': self.xrpeur_ob_callback,
                      'order_book_xrpbtc': self.xrpbtc_ob_callback}
  
          event = 'data'
          self._bind_channels(event, channels)
docs: Registers the binding for the order_book channels.
          :return: