def _expand_ellipsis(args, rank):
    """ Expand ellipsis objects and fill in missing axes.
    """
    n_el = sum(1 for arg in args if arg is Ellipsis)
    if n_el > 1:
        raise ValueError("Only one ellipsis may be used.")
    elif n_el == 0 and len(args) != rank:
        args = args + (Ellipsis,)

    final_args = []
    n_args = len(args)
    for arg in args:

        if arg is Ellipsis:
            final_args.extend( (slice(None,None,None),)*(rank-n_args+1) )
        else:
            final_args.append(arg)

    if len(final_args) > rank:
        raise TypeError("Argument sequence too long")

    return final_args