def fixed_anchor_init(dim: int):
    """
    Fixed anchors sizes for 2d and 3d

    Args:
        dim: number of dimensions

    Returns:
        dict: fixed params
    """
    anchor_plan = {"stride": 1, "aspect_ratios": (0.5, 1, 2)}
    if dim == 2:
        anchor_plan["sizes"] = (32, 64, 128, 256)
    else:
        anchor_plan["sizes"] = ((4, 8, 16), (8, 16, 32), (16, 32, 64), (32, 64, 128))
        anchor_plan["zsizes"] = ((2, 3, 4), (4, 6, 8), (8, 12, 16), (12, 24, 48))
    return anchor_plan