code: def disallowed_in_before_trading_start(exception):
      
      def decorator(method):
          @wraps(method)
          def wrapped_method(self, *args, **kwargs):
              if self._in_before_trading_start:
                  raise exception
              return method(self, *args, **kwargs)
          return wrapped_method
      return decorator
docs: Decorator for API methods that cannot be called from within
      TradingAlgorithm.before_trading_start.  `exception` will be raised if the
      method is called inside `before_trading_start`.
  
      Examples
      --------
      @disallowed_in_before_trading_start(SomeException("Don't do that!"))
      def method(self):
          # Do stuff that is not allowed inside before_trading_start.