def add_instance_groups(self, jobflow_id, instance_groups):
        """
        Adds instance groups to a running cluster.

        :type jobflow_id: str
        :param jobflow_id: The id of the jobflow which will take the
            new instance groups
            
        :type instance_groups: list(boto.emr.InstanceGroup)
        :param instance_groups: A list of instance groups to add to the job
        """
        if type(instance_groups) != types.ListType:
            instance_groups = [instance_groups]
        params = {}
        params['JobFlowId'] = jobflow_id
        params.update(self._build_instance_group_list_args(instance_groups))

        return self.get_object('AddInstanceGroups', params,
                               AddInstanceGroupsResponse, verb='POST')
Adds instance groups to a running cluster.

        :type jobflow_id: str
        :param jobflow_id: The id of the jobflow which will take the
            new instance groups
            
        :type instance_groups: list(boto.emr.InstanceGroup)
        :param instance_groups: A list of instance groups to add to the job