'Modify the number of nodes and configuration settings in an
instance group.
:type instance_group_ids: list(str)
:param instance_group_ids: A list of the ID\'s of the instance
groups to be modified
:type new_sizes: list(int)
:param new_sizes: A list of the new sizes for each instance group'

def modify_instance_groups(self, instance_group_ids, new_sizes):

    if (not isinstance(instance_group_ids, list)):
        instance_group_ids = [instance_group_ids]
    if (not isinstance(new_sizes, list)):
        new_sizes = [new_sizes]
    instance_groups = zip(instance_group_ids, new_sizes)
    params = {}
    for (k, ig) in enumerate(instance_groups):
        params[('InstanceGroups.member.%d.InstanceGroupId' % (k + 1))] = ig[0]
        params[('InstanceGroups.member.%d.InstanceCount' % (k + 1))] = ig[1]
    return self.get_object('ModifyInstanceGroups', params, ModifyInstanceGroupsResponse, verb='POST')
