When trying to write points3D from COLMAP documentation, what data type is required?

I am trying to iteratively write to .txt file using this python function from COLMAP, and i cannot fathom what data type it wants as an input. Is it a dict, tuple, colleciton, list of dicts?

Point3D = collections.namedtuple(
    "Point3D", ["id", "xyz", "rgb", "error", "image_ids", "point2D_idxs"])


def write_points3D_text(points3D, path):
    """
    see: src/base/reconstruction.cc
        void Reconstruction::ReadPoints3DText(const std::string& path)
        void Reconstruction::WritePoints3DText(const std::string& path)
    """
    if len(points3D) == 0:
        mean_track_length = 0
    else:
        mean_track_length = sum((len(pt.image_ids) for _, pt in points3D.items()))/len(points3D)

    HEADER = "# 3D point list with one line of data per point:\n" + \
             "#   POINT3D_ID, X, Y, Z, R, G, B, ERROR, TRACK[] as (IMAGE_ID, POINT2D_IDX)\n" + \
             "# Number of points: {}, mean track length: {}\n".format(len(points3D), mean_track_length)

    with open(path, "w") as fid:
        fid.write(HEADER)
        for _, pt in points3D.items():                         #dict?
            point_header = [pt.id, *pt.xyz, *pt.rgb, pt.error] #tuple? collection?
            fid.write(" ".join(map(str, point_header)) + " ")
            track_strings = []
            for image_id, point2D in zip(pt.image_ids, pt.point2D_idxs):
                track_strings.append(" ".join(map(str, [image_id, point2D])))
            fid.write(" ".join(track_strings) + "\n")