def controller(self):
        """
        Check if multiple controllers are connected.

        :returns: Return the controller_id of the active controller.
        :rtype: string
        """

        if hasattr(self, 'controller_id'):
            if len(self.controller_info['controllers']) > 1:
                raise TypeError(
                    'Only one controller per account is supported.'
                )
            return self.controller_id
        raise AttributeError('No controllers assigned to this account.')
Check if multiple controllers are connected.

        :returns: Return the controller_id of the active controller.
        :rtype: string