def all_gather(data, group=None):
    """
    Run all_gather on arbitrary picklable data (not necessarily tensors).

    Args:
        data: any picklable object
        group: a torch process group. By default, will use a group which
            contains all ranks on gloo backend.

    Returns:
        list[data]: list of data gathered from each rank
    """
    if get_world_size() == 1:
        return [data]
    if group is None:
        group = _get_global_gloo_group()  # use CPU group by default, to reduce GPU RAM usage.
    world_size = dist.get_world_size(group)
    if world_size == 1:
        return [data]

    output = [None for _ in range(world_size)]
    dist.all_gather_object(output, data, group=group)
    return output

    Run all_gather on arbitrary picklable data (not necessarily tensors).

    Args:
        data: any picklable object
        group: a torch process group. By default, will use a group which
            contains all ranks on gloo backend.

    Returns:
        list[data]: list of data gathered from each rank
    
EVA-02/det/detectron2/utils/comm.py