How to use the nitransforms.linear.load function in nitransforms

def concatenate_xfms(
    in_files, out_file, out_inv=None, reference=None, moving=None, fmt="itk"
):
    """Concatenate linear transforms."""
    xfm = TransformChain(
        [load_affine(f, fmt=XFM_FMT[Path(f).suffix]) for f in in_files]
    ).asaffine()
    if reference is not None and not xfm.reference:
        xfm.reference = reference

    xfm.to_filename(out_file, moving=moving, fmt=fmt)

    if out_inv is not None:
        inv_xfm = ~xfm
        if moving is not None:
            inv_xfm.reference = moving
        inv_xfm.to_filename(out_inv, moving=reference, fmt=fmt)